Fluid line autoconnect apparatus and methods for medical treatment system

ABSTRACT

A medical infusion fluid handling system, such as an automated peritoneal dialysis system, may be arranged to de-cap and connect one or more lines (such as solution lines) with one or more spikes or other connection ports on a fluid handling cassette. This feature may reduce a likelihood of contamination since no human interaction is required to de-cap and connect the one or more lines and the one or more spikes. For example, the automated peritoneal dialysis system may include a carriage arranged to receive the one or more lines each having a connector end and a cap. The carriage may move along a first direction so as to move the connector ends of the one or more lines along the first direction, and a cap stripper may be arranged to engage with the caps on the one or more lines on the carriage. The cap stripper may move in a second direction transverse to the first direction, as well as to move with the carriage along the first direction.

RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.12/864,287, which issued on May 5, 2015 as U.S. Pat No. 9,022,969, andwhich is a National Stage of International Patent Application No. PCT/US2009/000437, filed Jan 23, 2009, and entitled “FLUID LINE AUTOCONNECTAPPARATUS AND METHODS FOR MEDICAL TREATMENT SYSTEM,” which claimspriority under 35U.S.C. § 119(e) to U.S. Provisional Patent ApplicationNo. 61/011,967, filed Jan. 23, 2008, and entitled “PERITONEAL DIALYSISSYSTEMS, DEVICES AND METHODS,” and U.S. Provisional Patent ApplicationNo. 61/058,469, filed Jun. 3, 2008, and entitled “PERITONEAL DIALYSISSYSTEM.” Each of these applications is incorporated herein by referencein its entirety for all purposes.

BACKGROUND

Peritoneal Dialysis (PD) involves the periodic infusion of sterileaqueous solution (called peritoneal dialysis solution, or dialysate)into the peritoneal cavity of a patient. Diffusion and osmosis exchangestake place between the solution and the bloodstream across the naturalbody membranes. These exchanges transfer waste products to the dialysatethat the kidneys normally excrete. The waste products typically consistof solutes like sodium and chloride ions, and other compounds normallyexcreted through the kidneys like urea, creatinine, and water. Thediffusion of water across the peritoneal membrane during dialysis iscalled ultrafiltration.

Conventional peritoneal dialysis solutions include dextrose inconcentrations sufficient to generate the necessary osmotic pressure toremove water from the patient through ultrafiltration.

Continuous Ambulatory Peritoneal Dialysis (CAPD) is a popular form ofPD. A patient performs CAPD manually about four times a day. During adrain/fill procedure for CAPD, the patient initially drains spentperitoneal dialysis solution from his/her peritoneal cavity, and theninfuses fresh peritoneal dialysis solution into his/her peritonealcavity. This drain and fill procedure usually takes about 1 hour.

Automated Peritoneal Dialysis (APD) is another popular form of PD. APDuses a machine, called a cycler, to automatically infuse, dwell, anddrain peritoneal dialysis solution to and from the patient's peritonealcavity. APD is particularly attractive to a PD patient, because it canbe performed at night while the patient is asleep. This frees thepatient from the day-to-day demands of CAPD during his/her waking andworking hours.

The APD sequence typically lasts for several hours. It often begins withan initial drain phase to empty the peritoneal cavity of spentdialysate. The APD sequence then proceeds through a succession of fill,dwell, and drain phases that follow one after the other. Eachfill/dwell/drain sequence is called a cycle.

During the fill phase, the cycler transfers a predetermined volume offresh, warmed dialysate into the peritoneal cavity of the patient. Thedialysate remains (or “dwells”) within the peritoneal cavity for aperiod of time. This is called the dwell phase. During the drain phase,the cycler removes the spent dialysate from the peritoneal cavity.

The number of fill/dwell/drain cycles that are required during a givenAPD session depends upon the total volume of dialysate prescribed forthe patient's APD regimen, and is either entered as part of thetreatment prescription or calculated by the cycler.

APD can be and is practiced in different ways.

Continuous Cycling Peritoneal Dialysis (CCPD) is one commonly used APDmodality. During each fill/dwell/drain phase of CCPD, the cycler infusesa prescribed volume of dialysate. After a prescribed dwell period, thecycler completely drains this liquid volume from the patient, leavingthe peritoneal cavity empty, or “dry.” Typically, CCPD employs 4-8fill/dwell/drain cycles to achieve a prescribed therapy volume.

After the last prescribed fill/dwell/drain cycle in CCPD, the cyclerinfuses a final fill volume. The final fill volume dwells in the patientfor an extended period of time. It is drained either at the onset of thenext CCPD session in the evening, or during a mid-day exchange. Thefinal fill volume can contain a different concentration of dextrose thanthe fill volume of the successive CCPD fill/dwell/drain fill cycles thecycler provides.

Intermittent Peritoneal Dialysis (IPD) is another APD modality. IPD istypically used in acute situations, when a patient suddenly entersdialysis therapy. IPD can also be used when a patient requires PD, butcannot undertake the responsibilities of CAPD or otherwise do it athome.

Like CCPD, IPD involves a series of fill/dwell/drain cycles. UnlikeCCPD, IPD does not include a final fill phase. In IPD, the patient'speritoneal cavity is left free of dialysate (or “dry”) in between APDtherapy sessions.

Tidal Peritoneal Dialysis (TPD) is another APD modality. Like CCPD, TPDincludes a series of fill/dwell/drain cycles. Unlike CCPD, TPD does notcompletely drain dialysate from the peritoneal cavity during each drainphase. Instead, TPD establishes a base volume during the first fillphase and drains only a portion of this volume during the first drainphase. Subsequent fill/dwell/drain cycles infuse and then drain areplacement volume on top of the base volume. The last drain phaseremoves all dialysate from the peritoneal cavity.

There is a variation of TPD that includes cycles during which thepatient is completely drained and infused with a new full base volume ofdialysis.

TPD can include a final fill cycle, like CCPD. Alternatively, TPD canavoid the final fill cycle, like IPD.

APD offers flexibility and quality of life enhancements to a personrequiring dialysis. APD can free the patient from the fatigue andinconvenience that the day to day practice of CAPD represents to someindividuals. APD can give back to the patient his or her waking andworking hours free of the need to conduct dialysis exchanges.

Still, the complexity and size of past machines and associateddisposables for various APD modalities have dampened widespread patientacceptance of APD as an alternative to manual peritoneal dialysismethods.

SUMMARY OF INVENTION

Aspects of the invention relate to various components, systems andmethods for use in medical applications, including medical infusionoperations such as peritoneal dialysis. In some cases, aspects of theinvention are limited to applications in peritoneal dialysis, whileothers to more general dialysis applications (e.g., hemodialysis) orinfusion applications, while others to more general methods orprocesses. Thus, aspects of the invention are not necessarily limited toAPD systems and methods, although many of the illustrative embodimentsdescribed relate to APD.

In one aspect of the invention, a disposable fluid handling cassette,such as that useable with an APD cycler device or other infusionapparatus, includes a generally planar body having at least one pumpchamber formed as a depression in a first side of the body and aplurality of flowpaths for fluid that includes a channel. A patient lineport may be arranged for connection to a patient line and be in fluidcommunication with the at least one pump chamber via at least oneflowpath, and a membrane may be attached to the first side of the bodyover the at least one pump chamber. In one embodiment, the membrane mayhave a pump chamber portion with an unstressed shape that generallyconforms to the pump chamber depression in the body and is arranged tobe movable for movement of fluid in the useable space of the pumpchamber. If the cassette body include two or more pump chamberdepressions, the membrane may likewise include two or more pre-shapedpump portions. In other embodiments, the membrane need not be includedwith the cassette, e.g., where a control surface of the cycler interactswith the cassette to control pumping and/or valve functions.

In another embodiment, the pump chamber may include one or more spacerelements that extend from an inner wall of the depression, e.g., to helpprevent the membrane from contacting the inner wall, thereby preventingblocking of an inlet/outlet of the pump chamber, helping remove or trapair in the pump chamber, and/or preventing sticking of the membrane tothe inner wall. The spacer elements may be arranged to minimizedeformation of the membrane at edges of the spacer elements when themembrane is forced against the spacer elements.

In another embodiment, a patient line port and a drain line port may belocated at a first end of the body and be in fluid communication withthe at least one pump chamber via at least one flowpath. A plurality ofsolution line spikes may, on the other hand, be located at a second endof the body opposite the first end, with each of the solution linespikes being in fluid communication with the at least one pump chambervia at least one flowpath. This arrangement may enable automatedconnection of solution lines to the cassette, and/or separate occlusionof the patient and/or drain lines relative to the solution lines. In oneembodiment, a heater bag line port may also be located at the first endof the body and be in fluid communication with the at least one pumpchamber via at least one flowpath. Flexible patient, drain and heaterbag lines may be respectively connected to the patient line port, drainline port and heater bag line port.

In another embodiment, the body may include a vacuum vent clearancedepression formed adjacent the at least one pump chamber. Thisdepression may aid in the removal of fluid (gas and/or liquid) betweenthe membrane and a corresponding control surface of the cycler, e.g., byway of a vacuum port in the control surface. That is, the depression mayhelp ensure that the membrane is not forced against the vacuum port,leaving the port open to draw fluid into a collection chamber asnecessary.

In one embodiment, one or more ports, such as a drain line port andheater bag line port, and/or one or more solution line spikes maycommunicate with a common flowpath channel of the cassette base. Asneeded, a plurality of valves may each be arranged to control flow in arespective flowpath between the at least one pump chamber and thepatient line port, the drain line port, and the plurality of solutionline spikes. In one embodiment, portions of the membrane may bepositioned over respective valves and be movable to open and close therespective valve. Similarly, flow through openings into the pumpchamber(s) may be controlled by corresponding valves that are opened andclosed by movement of one or more portions of the membrane.

In some embodiments, the membrane may close at least some of theflowpaths of the body. That is, the body may be formed with open flowchannels that are closed on at least one side by the membrane. In oneembodiment, the body may include flowpaths formed on opposite planarsides, and at least some of the flowpaths on a first side maycommunicate with flowpaths on the second side.

In one embodiment, one or more spikes on the cassette (e.g., forreceiving dialysate solution) may be covered by a spike cap that sealsthe spike closed and is removable.

In another aspect of the invention, a disposable fluid handlingcassette, for use with a reusable automated peritoneal dialysis cyclerdevice, includes a generally planar body having at least one pumpchamber formed as a depression in a first side of the body and aplurality of flowpaths for fluid that includes a channel, a patient lineport arranged for connection to a patient line, the patient line portbeing in fluid communication with the at least one pump chamber via atleast one flowpath, and a flexible membrane attached to the first sideof the body over the at least one pump chamber. A pump chamber portionof the membrane over the at least one pump chamber may have anunstressed shape that generally conforms to usable area of the pumpchamber depression in the body and be arranged to be movable formovement of fluid in the pump chamber. In one embodiment, the cassetteis configured for operative engagement with a reusable automatedperitoneal dialysis cycler device.

The cassette may include a drain line port arranged for connection to adrain line, the drain line port being in fluid communication with the atleast one pump chamber via at least one flowpath, and/or a plurality ofsolution line spikes that are in fluid communication with the at leastone pump chamber via at least one flowpath. The pump chamber portion ofthe membrane may be generally dome shaped, and may include two pumpchamber portions that have a shape that generally conforms to usablearea of a corresponding pump chamber depression. In one embodiment, avolume of the pump chamber portion may be between 85-110% of the useablevolume of the pump chamber depression. In another embodiment, the pumpchamber portion may be arranged to be 85-110% of the depth of theuseable area of the pump chamber depression. In another embodiment, thepump chamber portion may be arranged to have a size that is between85-100% of the circumference of the useable area of the pump chamberdepression. The useable area of the pump chamber may be defined at leastin part by one or more spacer elements that extend from an inner wall ofthe depression. In one embodiment, a plurality of spacer elements may beof graduated lengths or varying height that define a generallydome-shaped region or other shape. The spacer elements may be arrangedin a concentric elliptical pattern or other shape when viewed in plan.One or more breaks in the pattern may be provided, e.g., to allowcommunication between voids. In one embodiment, the spacer elements maybe arranged to minimize deformation of the membrane at edges of thespacer elements when the membrane is forced against the spacer elements.In another embodiment, one or more spacers may be configured to inhibitthe membrane from covering the fluid inlet and/or outlet of the pumpchamber.

In another aspect of the invention, a fluid handling cassette for usewith a fluid handling system of a medical infusion device includes agenerally planar body having at least one pump chamber formed as adepression in a first side of the body and a plurality of flowpaths forfluid that includes a channel, the at least one pump chamber includingone or more spacer elements that extend from an inner wall of thedepression, a patient line port arranged for connection to a patientline, the patient line port being in fluid communication with the atleast one pump chamber via at least one flowpath, a drain line portarranged for connection to a drain line, the drain line port being influid communication with the at least one pump chamber via at least oneflowpath, and a plurality of solution line spikes being in fluidcommunication with the at least one pump chamber via at least oneflowpath.

In one aspect of the invention, a disposable component system for usewith a fluid line connection system of a peritoneal dialysis systemincludes a fluid handling cassette having a generally planar body withat least one pump chamber formed as a depression in a first side of thebody and a plurality of flowpaths for fluid, a solution line spikelocated at a first end of the body, the solution line spike being influid communication with the at least one pump chamber via at least oneflowpath, and a spike cap configured to removably cover the solutionline spike, wherein the cap includes at least one raised feature (e.g.,an asymmetrical or symmetrical flange) to aid in removal of the cap forconnection to a solution line prior to the commencement of a peritonealdialysis therapy.

In one embodiment, the cassette includes a skirt arranged around thespike to receive the end of the spike cap, and there may be a recessbetween the skirt and the spike that are arranged to aid in forming aseal between the spike cap and skirt.

In another embodiment, a solution line cap may be removably connected toa solution line, and the solution line cap may include a recessedfeature (such as a symmetrical or asymmetrical groove). At least aportion of the solution line cap may include a flexible material, suchas silicone rubber. The recessed feature may aid in the removal of aspike cap from the cassette.

In another embodiment, the spike cap includes a second raised featurethat may function as a stop for the solution line cap.

In another embodiment, a main axis of one or more spikes is insubstantially a same plane as the generally planar body of the fluidhandling cassette.

In another aspect of the invention, a fluid handling cassette for usewith a peritoneal dialysis system includes a generally planar body withat least one pump chamber formed as a depression in a first side of thebody and a plurality of flowpaths for fluid, and a spike located at afirst end of the body for engagement with a dialysate solution line. Thespike may be in fluid communication with the at least one pump chambervia at least one flowpath and include a distal tip and a lumen arrangedso that the distal tip of the spike is positioned substantially near thelongitudinal axis of the spike. In one embodiment, the lumen may bepositioned substantially off the longitudinal axis.

In another aspect of the invention, a disposable component system foruse with a fluid line connection system of a peritoneal dialysis systemincludes a spike cap configured to removably cover a spike of a fluidhandling cassette. The cap may include at least one feature to aid inremoval of the cap for connection to a solution line prior to thecommencement of a peritoneal dialysis therapy. The feature may be araised feature, or a recessed feature, and may be configured forengagement with a solution line cap.

In another aspect of the invention, a disposable component system foruse with a fluid line connection system of a peritoneal dialysis systemincludes a solution line cap for removable attachment to a solutionline, wherein the solution line cap includes at least one feature to aidin removal of a spike cap to enable connection between a solution lineand a spike prior to the commencement of a peritoneal dialysis therapy.The feature may be a raised feature, or a recessed feature, and may beconfigured for engagement with a spike cap. Indicia may be associatedwith a solution line, e.g., so that a solution associated with the linemay be identified and affect at least one function of the peritonealdialysis system.

In another aspect of the invention, a medical infusion fluid handlingsystem, such as an APD system, may be arranged to de-cap and connect oneor more lines (such as solution lines) with one or more spikes or otherconnection ports on a fluid handling cassette. This feature may provideadvantages, such as a reduced likelihood of contamination since no humaninteraction is required to de-cap and connect the lines and spikes. Forexample, an APD system may include a carriage arranged to receive aplurality of solution lines each having a connector end and a cap. Thecarriage may be arranged to move along a first direction so as to movethe connector ends of the solution lines along the first direction, anda cap stripper may be arranged to engage with caps on the solution lineson the carriage. The cap stripper may be arranged to move in a seconddirection transverse to the first direction, as well as to move with thecarriage along the first direction. For example, the carriage may movetoward a cassette in an APD cycler in a first direction so as to engagecaps on the solution lines with caps on spikes of the cassette. The capstripper may engage the caps (e.g., by moving in a direction transverseto the motion of the carriage) and then move with the carriage as thecarriage pulls away from the cassette to remove the caps from thespikes. The carriage may then pull the connector ends of the solutionlines from the caps on the cap stripper, which may retract to allow thecarriage to engage the now exposed solution line connector ends with theexposed spikes on the cassette.

In one embodiment, the carriage may include a plurality of grooves thateach receive a corresponding solution line. By positioning solutionlines in corresponding grooves, each of the lines may be more easilyindividually identified, e.g., by reading a barcode or other identifieron the line, and controlling the system accordingly. The carriage may bemounted to a door of a cycler housing, and a carriage drive may move thecarriage along the first direction. In one embodiment, the carriagedrive may engage the carriage when the door is moved to a closedposition, and disengage from the carriage when the door is moved to anopen position.

In one embodiment, the cap stripper may include a plurality offork-shaped elements arranged to engage with a corresponding cap on asolution line carried by the carriage. The fork-shaped elements may holdthe caps when they are removed from the solution lines, and each of thesolution line caps may itself hold a spike cap. In another embodiment,the cap stripper may include a plurality of rocker arms each associatedwith a fork-shaped element. Each of the rocker arms may be arranged tomove to engage a spike cap, e.g., to assist in removing the spike capfrom the corresponding spike. Each of the rocker arms may be arranged toengage with a corresponding spike cap only when the associatedfork-shaped element engages with a cap on a solution line. Thus, the capstripper may not engage or remove spike caps from the cassette inlocations where there is no corresponding solution line to connect withthe spike.

In another aspect of the invention, a method for connecting fluid linesin a medical infusion fluid handling system, such as an APD cycler, mayinvolve locating solution lines and spikes of a cassette in an enclosedspace away from human touch. The solution lines and/or spikes may havecaps removed and the lines connected to spikes while in the enclosedspace, thus providing the connection while minimizing potentialcontamination at the connection, e.g., by fingers carrying pathogens orother potentially harmful substances. For example, one method inaccordance with this aspect of the invention includes providing aplurality of solution lines each having a connector end and a cap,providing a fluid handling cassette having a plurality of spikes eachcovered by a spike cap, enclosing the connector ends of the plurality ofsolution lines with caps covering the connector ends and the pluralityof spikes with spike caps covering the spikes in a space that preventshuman touch of the caps or spike caps, removing the caps from theconnector ends of the plurality of solution lines without removing thecaps or connector ends from the space, removing the spike caps from thespikes without removing the spike caps or spikes from the space,engaging the caps with respective ones of the spike caps, and fluidlyconnecting the plurality of connector ends to corresponding spikes whilemaintaining the connector ends and spikes in the space and protectedfrom human touch.

In one embodiment, the solution line caps and spike caps may be engagedwith each other before their removal from the lines or spikes, and thenmay be removed from both the lines and the spikes while engaged witheach other. This technique may simplify the de-capping/capping process,as well as allow for easier storage of the caps.

In another embodiment, the solution lines may be disconnected from thespikes, and the connector ends of the lines and the spikes may bere-capped, e.g., after a treatment is completed.

In another aspect of the invention, a dialysis machine may include afluid handling cassette having a plurality of spikes and a plurality ofspike caps covering a respective spike, a plurality of solution lineseach having a cap covering a connector end of the respective line, and acap stripper arranged to remove one or more caps from a connector end ofa solution line, and remove one or more spike caps from a spike on thecassette while the one or more caps are secured to a corresponding oneof the spike caps. As discussed above, the machine may be arranged toautomatically fluidly connect a connector end of a solution line with acorresponding spike after the caps are removed.

In another aspect of the invention, a dialysis machine, such as an APDsystem, may include a cassette having a plurality of fluid spikes and aplurality of spike caps covering a respective spike, a carriage arrangedto receive a plurality of solution lines each having a cap covering aconnector end of the respective line, and a cap stripper arranged toengage one or more caps covering a connector end of a line. The carriageand cap stripper may be configured to engage one or more caps on aconnector end of a line while the one or more caps are engaged with acorresponding spike cap covering a spike on the cassette, and to removethe spike cap from the spike and the cap from the connector end of thesolution line, and to fluidly connect the spike and the connector end ofthe solution line after the caps are removed.

In another aspect of the invention, a dialysis machine may include a capstripper that is arranged to remove one or more caps on a connector endof a solution line, remove one or more spike caps from spikes on a fluidhandling cassette, and to retain and reattach the caps to the solutionlines and the spike caps to the spikes on the cassette.

In another aspect of the invention, a fluid line connection system for aperitoneal dialysis system includes a fluid handling cassette having agenerally planar body with at least one pump chamber formed as adepression in a first side of the body and a plurality of flowpaths forfluid, a plurality of dialysate solution line spikes located at a firstend of the body, the solution line spikes being in fluid communicationwith the at least one pump chamber via at least one flowpath andarranged so that the spikes are generally co-planar with the generallyplanar body of the fluid handing cassette, and a carriage arranged toreceive a plurality of solution lines, where each solution line has aconnector end. The carriage may be arranged to automatically fluidlyconnect a connector end of a solution line with a corresponding spike.

In one embodiment, the carriage is arranged to move the solution linesand respective caps along a first direction substantially parallel tothe generally planar body of the fluid handling cassette. A carriagedrive that moves the carriage only the first direction may include adrive element and a pneumatic bladder or screw drive to move the driveelement along the first direction. A cap stripper may be provided thatis arranged to remove one or more caps from a connector end of asolution line, and remove one or more spike caps from a spike on thecassette while the one or more caps are secured to a corresponding oneof the spike caps. In one embodiment, the cap stripper may be arrangedto r retain and reattach the caps to the solution lines and the spikecaps to the spikes on the cassette.

In another aspect of the invention, a peritoneal dialysis system mayinclude a cycler device with components suitable for controllingdelivery of dialysate to the peritoneal cavity of a patient. The cyclerdevice may have a housing that encloses at least some of the componentsand have a heater bag receiving section. (The term “heater bag” is usedherein to refer to any suitable container to heat dialysate, such as aflexible or rigid container, whether made of polymer, metal or othersuitable material.) A lid may be mounted to the housing and be movablebetween an open position in which a heater bag is placeable in theheater bag receiving section and a closed position in which the lidcovers the heater bag receiving section. Such an arrangement may allowfor faster or more efficient heating of dialysate in the heater bag,e.g., because heat may be retained by the lid. Also, the lid may helpprevent human touch of potentially hot surfaces.

In on embodiment, the dialysis system may include a fluid handlingcassette with a heater bag port attached to a heater bag line, a patientport attached to a patient line, and at least one pump chamber to movefluid in the patient line and the heater bag line. A heater bag may beattached to the heater bag line and be arranged for placement in theheater bag receiving section.

In another embodiment, the system may include an interface (such as avisual display with a touch screen component) that is movably mounted tothe housing and is movable between a first position in which theinterface is received in the heater bag receiving section, and a secondposition in which the interface is located out of the heater bagreceiving section (e.g., a position in which a user may interact withthe interface). Thus, the interface may be hidden from view when thesystem is idle, allowing the interface to be protected. Also, storingthe interface in the heater bag receiving section may make the systemmore compact, at least in an “as stored” condition.

In another aspect of the invention, a dialysis system includes a supplyof pneumatic pressure and/or vacuum suitable for controllingpneumatically-operated components of the system, apneumatically-operated component that is fluidly connected to the supplyof pneumatic pressure and/or vacuum, and a control system that providespneumatic pressure or vacuum to the pneumatically-operated component andsubsequently isolates the pneumatically-operated component from thesupply of pneumatic pressure or vacuum for a substantial period of timebefore again providing pneumatic pressure or vacuum to thepneumatically-operated component. Such an arrangement may be useful forcomponents that are actuated relatively infrequently, such as theoccluder arrangement described herein. Small motions of some componentsmay cause the component to emit noise that may be found bothersome by apatient. By isolating the component from the pneumatic pressure/vacuum,the component may avoid slight movement caused by variations in thesupply pressure/vacuum, e.g., resulting from draws on thepressure/vacuum by other system components. In one embodiment, thesubstantial period of time may be 5 minutes or more, 1 hour or more, 50%or more of a time period required to deliver or remove a volume ofdialysate suitable for a dialysis treatment with respect to a patient'speritoneal cavity, or other suitable periods.

In another aspect of the invention, a dialysis system includes a supplyof pneumatic pressure and/or vacuum suitable for controllingpneumatically-operated components of the system, apneumatically-operated component that is fluidly connected to the supplyof pneumatic pressure and/or vacuum, and a control system that providespneumatic pressure or vacuum to the pneumatically-operated component andcontrols the pneumatic pressure or vacuum so as to reduce noisegenerated by the pneumatically-operated component. For example, thepneumatically-operated component may include at least one moving part(such as a pump diaphragm), and the control system may reduce thepneumatic pressure or vacuum provided to the pneumatically-operatedcomponent so as to slow movement of the moving part as the moving partstops and/or changes direction (e.g., the pressure/vacuum may becontrolled to slow movement of the diaphragm before the diaphragmchanges direction). In another embodiment, a pulse width modulationcontrol of a pressure/vacuum supply valve may be used, e.g., to reducenoise emitted by moving parts of the valve.

In another aspect of the invention, a dialysis system includes a supplyof pneumatic pressure and vacuum suitable for controllingpneumatically-operated components of the system. A firstpneumatically-operated component may be fluidly connected to the supplyof pneumatic pressure and/or vacuum, and have a first output line torelease pneumatic pressure. A second pneumatically-operated componentmay be fluidly connected to the supply of pneumatic pressure and/orvacuum, and have a second output line to release pneumatic vacuum. Aspace, such as that defined by an accumulator, manifold orsound-insulated chamber, may be fluidly connected to both the first andsecond output lines. A control system may provide pneumatic pressure orvacuum to the pneumatically-operated components so that when the firstand second components release pressure/vacuum during operation, thereleased pressure/vacuum may be received into the common space (e.g., amanifold). In some circumstances, gas under positive pressure releasedby components may be balanced by negative pressure released by othercomponents, thus reducing noise generated.

In another aspect of the invention, a peritoneal dialysis system mayinclude a fluid handling cassette having a patient line fluidlyconnected to and leading from the peritoneal cavity of a patient, andwhich includes at least one pump chamber to move dialysate solution inthe patient line. A cycler device may be arranged to receive andinteract with the fluid handling cassette and cause the at least onepump chamber to move dialysate solution in the patient line. The cyclermay include a control system arranged to control the at least one pumpchamber to operate in a priming operation to force dialysate solutioninto the patient line so as to remove any air in the patient line, andmay be adapted to interact with two types of fluid handling cassettesthat differ with respect to a volume of the patient line connected tothe cassette body. A first type of cassette may have a relatively lowvolume patient line (e.g., for pediatric applications), and a secondtype of cassette may have a relatively high volume patient line (e.g.,for adult applications), and the control system may detect whether acassette received by the cycler is a first type or a second type and toadjust cycler operation accordingly.

In one embodiment, the control system may detect whether a cassettereceived by the cycler is a first type or a second type by determiningthe volume of the patient line during priming, and to adjust the amountof fluid moved through the cassette during operation of the system. Inanother embodiment, indicia, such as a barcode, on the cassette may bedetected by the cycler and cause the cycler to adjust a pumpingoperation based on the type of cassette.

In another aspect of the invention, a dialysis machine includes a fluidhandling cassette having a plurality of spikes and at least one pumpchamber to move fluid in the spikes, a plurality of solution lines eachengaged with a respective spike on the cassette, and a control systemthat reads indicia on each of the solution lines to determine a type foreach of the solution lines. The control system may adjust a pumpingoperation or other cycler operation based in the identity of one or moreof the solution lines. For example, a solution line may be identified asbeing an effluent sampling line and the pumping operation may beadjusted to direct used dialysate from a patient to the effluentsampling line during a drain cycle.

In another aspect of the invention, a method of automatically recoveringfrom a tilt condition in a dialysis system may include (A) detecting anangle of tilt of at least a portion of a dialysis system, the portion ofthe dialysis system including machinery for performing a dialysistherapy, (B) determining that a tilt condition exists in which the angleof tilt exceeds a predetermined threshold, (C) in response to (B),pausing the dialysis therapy, (D) monitoring the angle of tilt while thedialysis therapy is paused, (E) determining that the tilt condition nolonger exists, and (F) in response to (E), automatically resuming thedialysis therapy.

In another aspect of the invention, a patient data interface for adialysis system includes a device port comprising a recess in a chassisof at least a portion of the dialysis system and a first connectordisposed within the recess. A patient data storage device may include ahousing and a second connector coupled to the housing, where the secondconnector is adapted to be selectively coupled to the first connector.The recess may have a first shape and the housing may have a secondshape corresponding to the first shape such that when the first andsecond connectors are coupled, the housing of the patient data storagedevice is received at least partially within the recess. The first andsecond shapes may be irregular and the patient data storage device mayhave a verification code that is readable by the dialysis system toverify that the patient data storage device is of an expected typeand/or origin.

In another aspect of the invention, a method for providing peritonealdialysis includes delivering or withdrawing dialysate with respect tothe patient's peritoneal cavity at a first pressure, and adjusting apressure at which dialysate is delivered or withdrawn to minimizepatient sensation of dialysate movement. In one embodiment, the pressuremay be adjusted during a same fill or empty cycle of a peritonealdialysis therapy, and/or within different fill or empty cycles of aperitoneal dialysis therapy. For example, when withdrawing dialysatefrom a patient, the pressure at which dialysate is withdrawn may bereduced when an amount of dialysate remaining in the peritoneal cavitydrops below a threshold volume. Reducing the pressure (negative pressureor vacuum) near the end of a drain cycle may reduce the sensation thepatient may have of the dialysate withdrawal.

In another aspect of the invention, a method for providing peritonealdialysis includes providing a first solution to a patient's peritonealcavity using a reusable cycler device during a first treatment ofperitoneal dialysis, and providing a second solution to the patient'speritoneal cavity using the reusable cycler device during a secondtreatment of peritoneal dialysis immediately subsequent to the firsttreatment, where the second solution has a different chemical makeuprelative to the first solution. The different solutions may be createdby mixing liquid material from two or more solution containers that areconnected to the cycler (e.g., via a cassette mounted to the cycler).The solution containers may be automatically identified by the cycler,e.g., by reading a barcode, RFID tag, or other indicia.

In another aspect of the invention, a medical infusion system includes ahousing that encloses at least some of the components of the system, anda control surface attached to the housing and constructed and arrangedto control the operation of a fluid handling cassette that may beremovably mounted to the housing. The control surface may have aplurality of movable portions arranged to control fluid pumping andvalve operations of the cassette, and at least one of the movableportions may have an associated vacuum port arranged to draw fluid froma region near the movable portion.

In one embodiment, the control surface includes a sheet of resilientpolymer material, and each of the movable portions may have anassociated vacuum port. In another embodiment, the cassette includes amembrane that is positionable adjacent the control surface, and thevacuum port is arranged to remove fluid from a space between themembrane and the control surface. A liquid sensor may be arranged todetect liquid drawn into the vacuum port, e.g., in case the membraneruptures, allowing liquid to leak from the cassette.

In another aspect of the invention, a volume of fluid moved by a pump,such as a pump in an APD system, may be determined based on pressuremeasurement and certain known chamber and/or line volumes, but withoutdirect measurement of the fluid, such as by flow meter, weight, etc. Inone embodiment, a volume of a pump chamber having a movable element thatvaries the volume of the pump chamber may be determined by measuringpressure in the pump chamber, and a reference chamber both whileisolated from each other, and after the two chambers are fluidlyconnected so that pressures in the chambers may equalize. In oneembodiment, equalization of the pressures may be assumed to occur in anadiabatic way, e.g., a mathematical model of the system that is based onan adiabatic pressure equalization process may be used to determine thepump chamber volume. In another embodiment, pressures measured after thechambers are fluidly connected may be measured at a time before completeequalization has occurred, and thus the pressures for the pump andreference chambers measured after the chambers are fluidly connected maybe unequal, yet still be used to determine the pump chamber volume. Thisapproach may reduce a time between measurement of initial and finalpressures, thus reducing a time during which heat transfer may takeplace and reducing error that may be introduced given the adiabaticmodel used to determine the pump chamber volume.

In one aspect of the invention, a method for determining a volume offluid moved by a pump includes measuring a first pressure for a pumpcontrol chamber when the pump control chamber is isolated from areference chamber. The pump control chamber may have a volume thatvaries at least in part based on movement of a portion of the pump, suchas a pump membrane or diaphragm. A second pressure may be measured forthe reference chamber when the reference chamber is isolated from thepump control chamber. The reference chamber may have a known volume. Athird pressure associated with the pump control chamber after fluidlyconnecting the reference chamber and the pump control chamber may bemeasured, but the measurement may occur before substantial equalizationof pressures between the pump control and reference chambers hasoccurred. Similarly, a fourth pressure associated with the referencechamber after fluidly connecting the reference chamber and the pumpcontrol chamber may be measured, but before substantial equalization ofpressures between the pump control and reference chambers has occurred.A volume for the pump control chamber may be determined based on thefirst, second, third and fourth measured pressures.

In one embodiment, the third and fourth pressures are measured atapproximately a same time and the third and fourth pressures aresubstantially unequal to each other. For example, equalization of thepressures in the pump control and reference chambers may occur after anequalization time period once the pump control and reference chambersare fluidly connected, but the third and fourth pressures may bemeasured at a time after the pump control and reference chambers arefluidly connected that is approximately 10% to 50% of the equalizationtime period. Thus, the third and fourth pressures may be measured longbefore (in time sense) the pressures in the chambers have fullyequalized. In another embodiment, the third and fourth pressures may bemeasured at a time when the pressures in the chambers has reachedapproximately 50-70% equalization, e.g., the pressures in the chambershave changed from an initial value that is within about 50-70% of anequalized pressure value. Thus, a time period between measurement of thefirst and second pressures and measurement of the third and fourthpressures may be minimized.

In another embodiment, a model for determining the volume of the pumpcontrol chamber may incorporate an assumption that an adiabatic systemexists from a point in time when the first and second pressures aremeasured for the isolated pump control chamber and the reference chamberuntil a point in time when the third and fourth pressures are measured.

To determine a volume of fluid moved by the pump, the steps of measuringthe first, second, third and fourth pressures and the step ofdetermining may be performed for two different positions of a pumpmembrane to determine two different volumes for the pump controlchamber. A difference between the two different volumes may represent avolume of fluid delivered by the pump.

As mentioned above, this aspect of the invention may be used in anysuitable system, such as a system in which the pump is part of adisposable cassette and the pump control chamber is part of a dialysismachine used in a dialysis procedure.

In one embodiment, the first and/or second pressure may be selected froma plurality of pressure measurements as coinciding with a point in timeat which a pressure in the pump control chamber or reference chamber (asappropriate) first begins to change from a previously stable value. Forexample, the point in time may be identified based on a determination ofwhen a best fit line for a plurality of consecutive sets of measuredpressures first deviates from a constant slope. This approach may helpidentify initial pressures for the pump control and reference chambersthat are as late in time as possible, while reducing error in the pumpvolume determination.

In another embodiment, a technique may be used to identify an optimalpoint in time at which the third and fourth pressures are measured. Forexample, a plurality of pressure values for the pump control chamber maybe measured after the pump control and reference chambers are fluidlyconnected, and a plurality of change in volume values may be determinedfor the pump control chamber based on the plurality of pressure valuesfor the pump control chamber. Each of the plurality of change in volumevalues may corresponding to a unique point in time and a measuredpressure value for the pump chamber. In this case, the change in volumevalues are due to movement of an imaginary piston that is present at thevalve or other component that initially isolates the pump control andreference chambers, but moves upon opening of the valve or othercomponent. Thus, the pump chamber does not actually change size orvolume, but rather the change in volume is an imaginary condition due tothe pressures in the pump chamber and reference chamber being differentfrom each other initially. Similarly, a plurality of pressure values forthe reference chamber may be measured after the pump control andreference chambers are fluidly connected, and a plurality of change involume values for the reference chamber may be determined based on theplurality of pressure values for the reference chamber. Each of theplurality of change in volume values may correspond to a unique point intime and a measured pressure value for the reference chamber, and likethe change in volume values for the pump chamber, are a result ofmovement of an imaginary piston. A plurality of difference valuesbetween change in volume values for the pump control chamber and for thereference chamber may be determined, with each difference value beingdetermined for corresponding change in volume values for the pumpcontrol chamber and change in volume values for the reference chamber,i.e., the pairs of change in volume values for which a difference valueis determined correspond to a same or substantially same point in time.The difference values may be analyzed, and a minimum difference value(or a difference value that is below a desired threshold) may indicate apoint in time for which the third and fourth pressures should bemeasured. Thus, the third and fourth pressure values may be identifiedas being equal to the pump control chamber pressure value and thereference chamber pressure value, respectively, that correspond to adifference value that is a minimum or below a threshold.

In another embodiment, the pressures measured are pressures of a gaswithin the pump control chamber and the reference chamber, theequalization of pressures within the pump control chamber and referencechamber is assumed to occur adiabatically, the equalization of pressuresbetween the pump control chamber and reference chamber is assumed toinclude a change in the volume of a gas in the pump control chamber andreference chamber in equal but opposite directions, and the volume ofgas in the reference chamber at the time of the fourth pressuremeasurement is calculated from the known volume of the referencechamber, and the second and fourth pressures. The change in volume ofgas in the reference chamber may be assumed to be the difference betweenthe known volume of the reference chamber and the calculated value ofthe volume of gas in the reference chamber at the time of the fourthpressure measurement. Also, the change in volume of gas in the pumpcontrol chamber may be assumed to be the difference between the initialvolume of the pump control chamber and the volume of gas in the pumpcontrol chamber at the time of the third pressure measurement, whereinthe change in volume of gas in the pump control chamber is equal to butopposite the change in volume of gas in the reference chamber.

In another aspect of the invention, a method for determining a volume offluid moved by a pump includes providing a fluid pump apparatus having apump chamber separated from a pump control chamber by a movablemembrane, and a reference chamber that is fluidly connectable to thepump control chamber, adjusting a first pressure in the pump controlchamber to cause the membrane to move and thereby move fluid in the pumpchamber, isolating the reference chamber from the pump control chamberand establishing a second pressure in the reference chamber that isdifferent from a pressure in the pump control chamber, fluidlyconnecting the reference chamber and the pump control chamber toinitiate equalization of pressures in the pump control chamber and thereference chamber, and determining a volume for the pump control chamberbased on the first and second pressures, and an assumption that thepressures in the pump control and reference chambers initiateequalization in an adiabatic way.

In one embodiment, third and fourth pressures for the pump control andreference chambers, respectively, may be measured after fluidlyconnecting the reference chamber and the pump control chamber, and thethird and fourth pressures may be used to determine the volume for thepump control chamber. The third and fourth pressures may besubstantially unequal to each other. Similar to that mentioned above,the adjusting, isolating, fluidly connecting and determining steps maybe repeated, and a difference between the two determined volumes for thepump control chamber may be determined, where the difference representsa volume of fluid delivered by the pump.

In another embodiment, the pump is part of a disposable cassette and thepump control chamber is part of a dialysis machine used in a dialysisprocedure.

In another aspect of the invention, a medical infusion system includes apump control chamber, a control surface associated with the pump controlchamber so that at least a portion of the control surface is movable inresponse to a pressure change in the pump control chamber, a fluidhandling cassette having at least one pump chamber positioned adjacentthe control surface and arranged so that fluid in the at least one pumpchamber moves in response to movement of the portion of the controlsurface, a reference chamber that is fluidly connectable to the pumpcontrol chamber, and a control system arranged to adjust a pressure inthe pump control chamber and thus control movement of fluid in the pumpchamber of the fluid handling cassette. The control system may bearranged to measure a first pressure for the pump control chamber whenthe pump control chamber is isolated from the reference chamber, measurea second pressure for the reference chamber when the reference chamberis isolated from the pump control chamber, fluidly connect the pumpcontrol chamber and the reference chamber, measure third and fourthpressures associated with the pump control chamber and the referencechamber, respectively, after fluidly connecting the reference chamberand the pump control chamber, and determine a volume for the pumpcontrol chamber based on the first, second, third and fourth measuredpressures and a mathematical model that defines equalization of pressurein the pump control and reference chambers as occurring adiabaticallywhen the pump control and reference chambers are fluidly connected.

In one embodiment, the third and fourth pressures are substantiallyunequal to each other, e.g., the third and fourth pressures may bemeasured prior to substantial equalization of pressures in the pumpcontrol and reference chambers.

In another aspect of the invention, a method for determining a volume offluid moved by a pump includes measuring a first pressure for a pumpcontrol chamber when the pump control chamber is isolated from areference chamber, the pump control chamber having a volume that variesat least in part based on movement of a portion of the pump, measuring asecond pressure for the reference chamber when the reference chamber isisolated from the pump control chamber, measuring a third pressureassociated with both the pump control chamber and the reference chamberafter fluidly connecting the reference chamber and the pump controlchamber, and determining a volume for the pump control chamber based onthe first, second and third measured pressures.

In one embodiment, the third pressure may be measured after completeequalization of pressures in the pump control and reference chambers iscomplete. In one embodiment, a model used to determine the pump chambervolume may assume an adiabatic system in equalization of pressurebetween the pump chamber and the reference chamber.

In one aspect of the invention, a method for determining a presence ofair in a pump chamber includes measuring a pressure for a pump controlchamber when the pump control chamber is isolated from a referencechamber, the pump control chamber having a known volume and beingseparated from a pump chamber, that is at least partially filled withliquid, by a membrane, measuring a pressure for the reference chamberwhen the reference chamber is isolated from the pump control chamber,the reference chamber having a known volume, measuring a pressure afterfluidly connecting the reference chamber and the pump control chamberand prior to a time when the pressure in the chambers has equalized, anddetermining a presence or absence of an air bubble in the pump chamberbased on the measured pressures and known volumes.

In one embodiment, a model used to determine the presence or absence ofan air bubble assumes an adiabatic system from a point in time when thepressures are measured for the isolated pump control chamber and thereference chamber until a point in time after the chambers are fluidlyconnected. In another embodiment, the pressure for the pump controlchamber is measured with the membrane drawn toward a wall of the pumpcontrol chamber.

In another aspect of the invention, an automated peritoneal dialysissystem includes a reusable cycler that is constructed and arranged forcoupling to a disposable fluid handling cassette containing at least onepumping chamber. The disposable fluid handling cassette may beconfigured to be connected in fluid communication with the peritoneum ofa patient via a first collapsible tube and with a second source and/ordestination (such as a solution container line) via a second collapsibletube. An occluder may be configured and positioned within the cycler toselectively occlude the first collapsible tube while not occluding thesecond collapsible tube. In one embodiment, the occluder can occlude aplurality of collapsible tubes, such as a patient line, a drain lineand/or a heater bag line. The cassette may have a generally planar bodywith at least one pump chamber formed as a depression in a first side ofthe body and a plurality of flowpaths for fluid, a patient line portlocated at a first end of the body arranged for connection to the firstcollapsible tube, and a solution line port located at a second end ofthe body opposite the first end, and arranged for connection to thesecond collapsible tube. The occluder may be configured and positionedwithin the cycler to selectively occlude the first tube and a thirdcollapsible tube (e.g., for a drain) while not occluding the secondcollapsible tube.

In another embodiment, the occluder includes first and second opposedoccluding members pivotally connected to each other, a tube contactingmember connected to, or comprising at least a portion of, at least oneof the first and second occluding members, and a force actuatorconstructed and positioned to apply a force to at least one of the firstand second occluding members. Application of the force by the forceactuator may cause the tube contacting members to move between a tubeoccluding and an open position. The occluder may include a releasemember configured and positioned to enable an operator to manually movethe tube contacting member from the tube occluding position to the openposition even with no force applied to the occluding member by the forceactuator. The force actuator may apply a force sufficient to bend boththe first and second occluding members, so that upon application of theforce by the force actuator to bend the first and second occludingmembers, the tube contacting member may move between a tube occludingand an open position. The occluding members may be spring platespivotally connected together at opposite first and second ends, and thetube contacting member may be a pinch head connected to the springplates at the first ends, while the second ends of the spring plates maybe affixed directly or indirectly to a housing to which the occluder isconnected. In one embodiment, the force actuator comprises an inflatablebladder positioned between the first and second occluding members. Theforce actuator may increase a distance between the first and secondoccluding members in a region where the first and second occludingmembers are in opposition so as to move the tube contacting memberbetween a tube occluding and an open position. In one embodiment, theforce actuator may bend one or both of the occluding members to move thetube contacting member from a tube occluding position to an openposition.

Various aspects of the invention are described above and below withreference to illustrative embodiments. It should be understood that thevarious aspects of the invention may be used alone and/or in anysuitable combination with other aspects of the invention. For example,the pump volume determination features described herein may be used witha liquid handling cassette having the specific features described, orwith any other suitable pump configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention are described below with reference toillustrative embodiments that are shown, at least in part, in thefollowing figures, in which like numerals reference like elements, andwherein:

FIG. 1 shows a schematic view of an automated peritoneal dialysis (APD)system that incorporates one or more aspects of the invention;

FIG. 2 is a schematic view of an illustrative set for use with the APDsystem of FIG. 1;

FIG. 3 is an exploded perspective view of a cassette in a firstembodiment;

FIG. 4 is a cross sectional view of the cassette along the line 4-4 inFIG. 3;

FIG. 5 is a perspective view of a vacuum mold that may be used to form amembrane having pre-formed pump chamber portions in an illustrativeembodiment;

FIG. 6 shows a front view of the cassette body of FIG. 3;

FIG. 7 is a front view of a cassette body including two different spacerarrangements in an illustrative embodiment;

FIG. 8 is a rear perspective view of the cassette body of FIG. 3;

FIG. 9 is a rear view of the cassette body of FIG. 3;

FIG. 10 is a perspective view of the APD system of FIG. 1 with the doorof the cycler in an open position;

FIG. 11 is a perspective view of the inner side of the door of thecycler show in FIG. 10;

FIG. 12 is a right front perspective view of a carriage drive assemblyand cap stripper in a first embodiment;

FIG. 13 a left front perspective view of the carriage drive assembly andcap stripper of FIG. 12;

FIG. 14 is a partial rear view of the carriage drive assembly of FIG.12;

FIG. 15 is a rear perspective view of a carriage drive assembly in asecond illustrative embodiment;

FIG. 16 is a left rear perspective view of the carriage drive assemblyand cap stripper of FIG. 15;

FIG. 17 is a left front perspective view of a cap stripper element in anillustrative embodiment;

FIG. 18 is a right front perspective view of the cap stripper element ofFIG. 17;

FIG. 19 is a front view of the cap stripper element of FIG. 17;

FIG. 20 is a cross sectional view along the line 20-20 in FIG. 19;

FIG. 21 is a cross sectional view along the line 21-21 in FIG. 19;

FIG. 22 is a cross sectional view along the line 22-22 in FIG. 19;

FIG. 23 is a close-up exploded view of the connector end of a solutionline in an illustrative embodiment;

FIG. 24 is a schematic view of a cassette and solution lines beingloaded into the cycler of FIG. 10;

FIG. 25 is a schematic view of the cassette and solution lines afterplacement in respective locations of the door of the cycler of FIG. 10;

FIG. 26 is a schematic view of the cassette and solution lines after thedoor of the cycler is closed;

FIG. 27 is a schematic view of the solution lines being engaged withspike caps;

FIG. 28 is a schematic view of the cap stripper engaging with spike capsand solution line caps;

FIG. 29 is a schematic view of the solution lines with attached caps andspike caps after movement away from the cassette;

FIG. 30 is a schematic view of the solution lines after movement awayfrom the solution line caps and spike caps;

FIG. 31 is a schematic view of the cap stripper retracting with thesolution line caps and spike caps;

FIG. 32 is a schematic view of the solution lines being engaged with thespikes of the cassette;

FIG. 33 is a cross sectional view of a cassette with five stages of asolution line connection operation shown with respect to correspondingspikes of the cassette;

FIG. 34 shows a rear view of a cassette in another illustrativeembodiment including different arrangements for a rear side of thecassette adjacent the pump chambers;

FIG. 35 shows an end view of a spike of a cassette in an illustrativeembodiment;

FIG. 36 shows a front view of a control surface of the cycler forinteraction with a cassette in the FIG. 10 embodiment;

FIG. 37 shows an exploded view of an assembly for the interface of FIG.36;

FIG. 38 shows an exploded perspective view of an occluder in anillustrative embodiment;

FIG. 39 shows a partially exploded perspective view of the occluder ofFIG. 38;

FIG. 40 shows a top view of the occluder of FIG. 38 with the bladder ina deflated state;

FIG. 41 shows a top view of the occluder of FIG. 38 with the bladder inan inflated state;

FIG. 42 is a schematic view of a pump chamber of a cassette andassociated control components and inflow/outflow paths in anillustrative embodiment;

FIG. 43 is a plot of illustrative pressure values for the controlchamber and the reference chamber from a point in time before opening ofthe valve X2 until some time after the valve X2 is opened for theembodiment of FIG. 42;

FIG. 44 is a perspective view of an interior section of the cycler ofFIG. 10 with the upper portion of the housing removed;

FIG. 45 is a schematic block diagram illustrating an exemplaryimplementation of control system for an APD system;

FIG. 46 is a schematic block diagram of illustrative software subsystemsof a user interface computer and the automation computer for the controlsystem of FIG. 45;

FIG. 47 shows a flow of information between various subsystems andprocesses of the APD system in an illustrative embodiment;

FIG. 48 illustrates an operation of the therapy subsystem of FIG. 46;

FIG. 49 shows a sequence diagram depicting exemplary interactions oftherapy module processes during initial replenish and dialyze portionsof the therapy;

FIGS. 50-55 show exemplary screen views relating to alerts and alarmsthat may be displayed on a touch screen user interface for the APDsystem;

FIG. 56 illustrates component states and operations for error conditiondetection and recovery in an illustrative embodiment;

FIG. 57 shows exemplary modules of a UI view subsystem for the APDsystem;

FIGS. 58-64 shows illustrative user interface screens for providing userinformation and receiving user input in illustrative embodimentsregarding system setup, therapy status, display settings, remoteassistance, and parameter settings; and

FIG. 65 shows an exemplary patient data key and associated port fortransferring patient data to and from the APD system.

DETAILED DESCRIPTION

Although aspects of the invention are described in relation to aperitoneal dialysis system, certain aspects of the invention can be usedin other medical applications, including infusion systems such asintravenous infusion systems or extracorporeal blood flow systems, andirrigation and/or fluid exchange systems for the stomach, intestinaltract, urinary bladder, pleural space or other body or organ cavity.Thus, aspects of the invention are not limited to use in peritonealdialysis in particular, or dialysis in general.

APD System

FIG. 1 shows an automated peritoneal dialysis (APD) system 10 that mayincorporate one or more aspects of the invention. As shown in FIG. 1,for example, the system 10 in this illustrative embodiment includes adialysate delivery set 12 (which, in certain embodiments, can be adisposable set), a cycler 14 that interacts with the delivery set 12 topump liquid provided by a solution container 20 (e.g., a bag), and acontrol system 16 (e.g., including a programmed computer or other dataprocessor, computer memory, an interface to provide information to andreceive input from a user or other device, one or more sensors,actuators, relays, pneumatic pumps, tanks, a power supply, and/or othersuitable components—only a few buttons for receiving user control inputare shown in FIG. 1, but further details regarding the control systemcomponents are provided below) that governs the process to perform anAPD procedure. In this illustrative embodiment, the cycler 14 and thecontrol system 16 are associated with a common housing 82, but may beassociated with two or more housings and/or may be separate from eachother. The cycler 14 may have a compact footprint, suited for operationupon a table top or other relatively small surface normally found in thehome. The cycler 14 may be lightweight and portable, e.g., carried byhand via handles at opposite sides of the housing 82.

The set 12 in this embodiment is intended to be a single use, disposableitem, but instead may have one or more reusable components, or may bereusable in its entirety. The user associates the set 12 with the cycler14 before beginning each APD therapy session, e.g., by mounting acassette 24 within a front door 141 of the cycler 14, which interactswith the cassette 24 to pump and control fluid flow in the various linesof the set 12. For example, dialysate may be pumped both to and from thepatient to effect APD. Post therapy, the user may remove all or part ofthe components of the set 12 from the cycler 14.

As is known in the art, prior to use, the user may connect a patientline 34 of the set 12 to his/her indwelling peritoneal catheter (notshown) at a connection 36. In one embodiment, the cycler 14 may beconfigured to operate with one or more different types of cassettes 24,such as those having differently sized patient lines 34. For example,the cycler 14 may be arranged to operate with a first type of cassettewith a patient line 34 sized for use with an adult patient, and a secondtype of cassette with a patient line 34 sized for an infant or pediatricuse. The pediatric patient line 34 may be shorter and have a smallerinner diameter than the adult line so as to minimize the volume of theline, allowing for more controlled delivery of dialysate and helping toavoid returning a relatively large volume of used dialysate to thepediatric patient when the set 12 is used for consecutive drain and fillcycles. A heater bag 22, which is connected to the cassette 24 by a line26, may be placed on a heater container receiving portion (in this case,a tray) 142 of the cycler 14. The cycler 14 may pump fresh dialysate(via the cassette 24) into the heater bag 22 so that the dialysate maybe heated by the heater tray 142, e.g., by electric resistance heatingelements associated with the tray 142 to a temperature of about 37degrees C. Heated dialysate may be provided from the heater bag 22 tothe patient via the cassette 24 and the patient line 34. In analternative embodiment, the dialysate can be heated on its way to thepatient as it enters, or after it exits, the cassette 24 by passing thedialysate through tubing in contact with the heater tray 142, or throughan in-line fluid heater (which may be provided in the cassette 24). Useddialysate may be pumped from the patient via the patient line 34 to thecassette 24 and into a drain line 28, which may include one or moreclamps to control flow through one or more branches of the drain line28. In this illustrative embodiment, the drain line 28 may include aconnector 39 for connecting the drain line 28 to a dedicated drainreceptacle, and an effluent sample port 282 for taking a sample of useddialysate for testing or other analysis. The user may also mount thelines 30 of one or more containers 20 within the door 141. The lines 30may also be connected to a continuous or real-time dialysate preparationsystem. (The lines 26, 28, 30, 34 may include a flexible tubing and/orsuitable connectors and other components (such as pinch valves, etc.) asdesired.) The containers 20 may contain sterile peritoneal dialysissolution for infusion, or other materials (e.g., materials used by thecycler 14 to formulate dialysate by mixing with water, or admixingdifferent types of dialysate solutions). The lines 30 may be connectedto spikes 160 of the cassette 24, which are shown in FIG. 1 covered byremovable caps. In one aspect of the invention described in more detailbelow, the cycler 14 may automatically remove caps from one or morespikes 160 of the cassette 24 and connect lines 30 of solutioncontainers 20 to respective spikes 160. This feature may help reduce thepossibility of infection or contamination by reducing the chance ofcontact of non-sterile items with the spikes 160.

With various connections made, the control system 16 may pace the cycler14 through a series of fill, dwell, and/or drain cycles typical of anAPD procedure. For example, during a fill phase, the cycler 14 may pumpdialysate (by way of the cassette 24) from one or more containers 20 (orother source of dialysate supply) into the heater bag 22 for heating.Thereafter, the cycler 14 may infuse heated dialysate from the heaterbag 22 through the cassette 24 and into the patient's peritoneal cavityvia the patient line 34. Following a dwell phase, the cycler 14 mayinstitute a drain phase, during which the cycler 14 pumps used dialysatefrom the patient via the line 34 (again by way of the cassette 24), anddischarges spent dialysis solution into a nearby drain (not shown) viathe drain line 28.

The cycler 14 does not necessarily require the solution containers 20and/or the heater bag 22 to be positioned at a prescribed head heightabove the cycler 14, e.g., because the cycler 14 is not necessarily agravity flow system. Instead, the cycler 14 may emulate gravity flow, orotherwise suitably control flow of dialysate solution, even with thesource solution containers 20 above, below or at a same height as thecycler 14, with the patient above or below the cycler, etc. For example,the cycler 14 can emulate a fixed head height during a given procedure,or the cycler 14 can change the effective head height to either increaseor decrease pressure applied to the dialysate during a procedure. Thecycler 14 may also adjust the rate of flow of dialysate. In one aspectof the invention, the cycler 14 may adjust the pressure and/or flow rateof dialysate when provided to the patient or drawn from the patient soas to reduce the patient's sensation of the fill or drain operation.Such adjustment may occur during a single fill and/or drain cycle, ormay be adjusted across different fill and/or drain cycles. In oneembodiment, the cycler 14 may taper the pressure used to draw useddialysate from the patient near the end of a drain operation. Becausethe cycler 14 may establish an artificial head height, it may have theflexibility to interact with and adapt to the particular physiology orchanges in the relative elevation of the patient.

Cassette

In one aspect of the invention, a cassette 24 may include patient anddrain lines that are separately occludable with respect to solutionsupply lines. That is, safety critical flow to and from patient line maybe controlled, e.g., by pinching the lines to stop flow, without theneed to occlude flow through one or more solution supply lines. Thisfeature may allow for a simplified occluder device since occlusion maybe performed with respect to only two lines as opposed to occludingother lines that have little or no effect on patient safety. Forexample, in a circumstance where a patient or drain connection becomesdisconnected, the patient and drain lines may be occluded. However, thesolution supply and/or heater bag lines may remain open for flow,allowing the cycler 14 to prepare for a next dialysis cycle; e.g.,separate occlusion of patient and drain lines may help ensure patientsafety while permitting the cycler 14 to continue to pump dialysate fromone or more containers 20 to the heater bag 22 or to other solutioncontainers 20.

In another aspect of the invention, the cassette may have patient, drainand heater bag lines at one side or portion of the cassette and one ormore solution supply lines at another side or portion of the cassette,e.g., an opposite side of the cassette. Such an arrangement may allowfor separate occlusion of patient, drain or heater bag lines withrespect to solution lines as discussed above. Physically separating thelines attached to the cassette by type or function allows for moreefficient control of interaction with lines of a certain type orfunction. For example, such an arrangement may allow for a simplifiedoccluder design because less force is required to occlude one, two orthree of these lines than all lines leading to or away from thecassette. Alternately, this arrangement may allow for more effectiveautomated connection of solution supply lines to the cassette, asdiscussed in more detail below. That is, with solution supply lines andtheir respective connections located apart from patient, drain and/orheater bag lines, an automated de-capping and connection device mayremove caps from spikes on the cassette as well as caps on solutionsupply lines, and connect the lines to respective spikes withoutinterference by the patient, drain or heater bag lines.

FIG. 2 shows an illustrative embodiment of a cassette 24 thatincorporates aspects of the invention described above. In thisembodiment, the cassette 24 has a generally planar body and the heaterbag line 26, the drain line 28 and the patient line 34 are connected atrespective ports on the left end of the cassette body, while the rightend of the cassette body may include five spikes 160 to which solutionsupply lines 30 may be connected. In the arrangement shown in FIG. 2,each of the spikes 160 is covered by a spike cap 63, which may beremoved, exposing the respective spike and allowing connection to arespective line 30. As described above, the lines 30 may be attached toone or more solution containers or other sources of material, e.g., foruse in dialysis and/or the formulation of dialysate, or connected to oneor more collection bags for sampling purposes or for peritonealequilibration testing (PET test).

FIGS. 3 and 4 show exploded views (perspective and top views,respectively) of the cassette 24 in this illustrative embodiment. Thecassette 24 is formed as a relatively thin and flat member having agenerally planar shape, e.g., may include components that are molded,extruded or otherwise formed from a suitable plastic. In thisembodiment, the cassette 24 includes a base member 18 that functions asa frame or structural member for the cassette 24 as well as forming, atleast in part, various flow channels, ports, valve portions, etc. Thebase member 18 may be molded or otherwise formed from a suitable plasticor other material, such as a polymethyl methacrylate (PMMA) acrylic, ora cyclic olefin copolymer/ultra low density polyethylene (COC/ULDPE),and may be relatively rigid. In an embodiment, the ratio of COC to ULDPEcan be approximately 85%/15%. FIG. 3 also shows the ports for the heaterbag (port 150), drain (port 152) and the patient (port 154) that areformed in the base member 18. Each of these ports may be arranged in anysuitable way, such as, for example, a central tube 156 extending from anouter ring or skirt 158, or a central tube alone. Flexible tubing foreach of the heater bag, drain and patient lines 26, 28, 34 may beconnected to the central tube 156 and engaged by the outer ring 158, ifpresent.

Both sides of the base member 18 may be covered, at least in part, by amembrane 15 and 16, e.g., a flexible polymer film made from, forexample, polyvinyl chloride (PVC), that is cast, extruded or otherwiseformed. Alternatively, the sheet may be formed as a laminate of two ormore layers of poly-cyclohexylene dimethylene cyclohexanedicarboxylate(PCCE) and/or ULDPE, held together, for example, by a coextrudableadhesive (CXA). In some embodiments, the membrane thickness may be inthe range of approximately 0.002 to 0.020 inches thick. In a preferredembodiment, the thickness of a PVC-based membrane may be in the range ofapproximately 0.012 to 0.016 inches thick, and more preferablyapproximately 0.014 inches thick. In another preferred embodiment, suchas, for example, for laminate sheets, the thickness of the laminate maybe in the range of approximately 0.006 to 0.010 inches thick, and morepreferably approximately 0.008 inches thick.

Both membranes 15 and 16 may function not only to close or otherwiseform a part of flowpaths of the cassette 24, but also may be moved orotherwise manipulated to open/close valve ports and/or to function aspart of a pump diaphragm, septum or wall that moves fluid in thecassette 24. For example, the membranes 15 and 16 may be positioned onthe base member 18 and sealed (e.g., by heat, adhesive, ultrasonicwelding or other means) to a rim around the periphery of the base member18 to prevent fluid from leaking from the cassette 24. The membrane 15may also be bonded to other, inner walls of the base member 18, e.g.,those that form various channels, or may be pressed into sealing contactwith the walls and other features of the base member 18 when thecassette 24 suitably mounted in the cycler 14. Thus, both of themembranes 15 and 16 may be sealed to a peripheral rim of the base member18, e.g., to help prevent leaking of fluid from the cassette 24 upon itsremoval from the cycler 14 after use, yet be arranged to lie,unattached, over other portions of the base member 18. Once placed inthe cycler 14, the cassette 24 may be squeezed between opposed gasketsor other members so that the membranes 15 and 16 are pressed intosealing contact with the base member 18 at regions inside of theperiphery, thereby suitably sealing channels, valve ports, etc., fromeach other.

Other arrangements for the membranes 15 and 16 are possible. Forexample, the membrane 16 may be formed by a rigid sheet of material thatis bonded or otherwise made integral with the body 18. Thus, themembrane 16 need not necessarily be, or include, a flexible member.Similarly, the membrane 15 need not be flexible over its entire surface,but instead may include one or more flexible portions to permit pumpand/or valve operation, and one or more rigid portions, e.g., to closeflowpaths of the cassette 24. It is also possible that the cassette 24may not include the membrane 16 or the membrane 15, e.g., where thecycler 14 includes a suitable member to seal pathways of the cassette,control valve and pump function, etc.

In accordance with another aspect of the invention, the membrane 15 mayinclude a pump chamber portion 151 (“pump membrane”) that is formed tohave a shape that closely conforms to the shape of a corresponding pumpchamber 181 depression in the base 18. For example, the membrane 15 maybe generally formed as a flat member with thermoformed (or otherwiseformed) dome-like shapes 151 that conform to the pump chamberdepressions of the base member 18. The dome-like shape of the pre-formedpump chamber portions 151 may be constructed, for example, by heatingand forming the membrane over a vacuum form mold of the type shown inFIG. 5. As shown in FIG. 5, the vacuum may be applied through acollection of holes along the wall of the mold. Alternatively, the wallof the mold can be constructed of a porous gas-permeable material, whichmay result in a more uniformly smooth surface of the molded membrane. Inthis way, the membrane 15 may move relative to the pump chambers 181 toeffect pumping action without requiring stretching of the membrane 15(or at least minimal stretching of the membrane 15), both when themembrane 15 is moved maximally into the pump chambers 181 and(potentially) into contact with spacer elements 50 (e.g., as shown insolid line in FIG. 4 while pumping fluid out of the pump chamber 181),and when the membrane 15 is maximally withdrawn from the pump chamber181 (e.g., as shown in dashed line in FIG. 4 when drawing fluid into thepump chamber 181). Avoiding stretching of the membrane 15 may helpprevent pressure surges or other changes in fluid delivery pressure dueto sheet stretch and/or help simplify control of the pump when seekingto minimize pressure variation during pump operation. Other benefits maybe found, including reduced likelihood of membrane 15 failure (e.g., dueto tears in the membrane 15 resulting from stresses place on themembrane 15 during stretching), and/or improved accuracy in pumpdelivery volume measurement, as described in more detail below. In oneembodiment, the pump chamber portions 151 may be formed to have a size(e.g., a define a volume) that is about 85-110% of the pump chamber 181,e.g., if the pump chamber portions 151 define a volume that is about100% of the pump chamber volume, the pump chamber portion 151 may lie inthe pump chamber 181 and in contact with the spacers 50 while at restand without being stressed.

Providing greater control of the pressure used to generate a fill anddelivery stroke of liquid into and out of a pump chamber may haveseveral advantages. For example, it may be desirable to apply theminimum negative pressure possible when the pump chamber draws fluidfrom the patient's peritoneal cavity during a drain cycle. A patient mayexperience discomfort during the drain cycle of a treatment in partbecause of the negative pressure being applied by the pumps during afill stroke. The added control that a pre-formed membrane can provide tothe negative pressure being applied during a fill stroke may help toreduce the patient's discomfort.

A number of other benefits may be realized by using pump membranespre-formed to the contour of the cassette pump chamber. For example, theflow rate of liquid through the pump chamber can be made more uniform,because a constant pressure or vacuum can be applied throughout the pumpstroke, which in turn may simplify the process of regulating the heatingof the liquid. Moreover, temperature changes in the cassette pump mayhave a smaller effect on the dynamics of displacing the membrane, aswell as the accuracy of measuring pressures within the pump chambers. Inaddition, pressure spikes within the fluid lines can be minimized. Also,correlating the pressures measured by pressure transducers on thecontrol (e.g. pneumatic) side of the membrane with the actual pressureof the liquid on the pump chamber side of the membrane may be simpler.This in turn may permit more accurate head height measurements of thepatient and fluid source bags prior to therapy, improve the sensitivityof detecting air in the pump chamber, and improve the accuracy ofvolumetric measurements. Furthermore, eliminating the need to stretchthe membrane may allow for the construction and use of pump chambershaving greater volumes.

In this embodiment, the cassette 24 includes a pair of pump chambers 181that are formed in the base member 18, although one pump chamber or morethan two pump chambers are possible. In accordance with an aspect of theinvention, the inner wall of pump chambers 181 includes spacer elements50 that are spaced from each other and extend from the inner wall ofpump chamber 18 to help prevent portions of the membrane 15 fromcontacting the inner wall of pump chamber 181. (As shown on theright-side pump chamber 181 in FIG. 4, the inner wall is defined by sideportions 181 a and a bottom portion 181 b. The spacers 50 extendupwardly from the bottom portion 181 b in this embodiment, but couldextend from the side portions 181 a or be formed in other ways.) Bypreventing contact of the membrane 15 with the pump chamber inner wall,the spacer elements 50 may provide a dead space (or trap volume) whichmay help trap air or other gas in the pump chamber 181 and inhibit thegas from being pumped out of the pump chamber 181 in some circumstances.In other cases, the spacers 50 may help the gas move to an outlet of thepump chamber 181 so that the gas may be removed from the pump chamber181, e.g., during priming. Also, the spacers 50 may help prevent themembrane 15 from sticking to the pump chamber inner wall and/or allowflow to continue through the pump chamber 181, even if the membrane 15is pressed into contact with the spacer elements 50. In addition, thespacers 50 help to prevent premature closure of the outlet port of thepump chamber (openings 187 and/or 191) if the sheet happens to contactthe pump chamber inner wall in a non-uniform manner. Further detailsregarding the arrangement and/or function of spacers 50 are provided inU.S. Pat. Nos. 6,302,653 and 6,382,923, both of which are incorporatedherein by reference.

In this embodiment, the spacer elements 50 are arranged in a kind of“stadium seating” arrangement such that the spacer elements 50 arearranged in a concentric elliptical pattern with ends of the spacerelements 50 increasing in height from the bottom portion 181 b of theinner wall with distance away from the center of the pump chamber 181 toform a semi-elliptical domed shaped region (shown by dotted line in FIG.4). Positioning spacer elements 50 such that the ends of the spacerelements 50 form a semi-elliptical region that defines the domed regionintended to be swept by the pump chamber portion 151 of the membrane 15may allow for a desired volume of dead space that minimizes anyreduction to the intended stroke capacity of pump chambers 181. As canbe seen in FIG. 3 (and FIG. 6), the “stadium seating” arrangement inwhich spacer elements 50 are arranged may include “aisles” or breaks 50a in the elliptical pattern. Breaks (or aisles) 50 a help to maintain anequal gas level throughout the rows (voids or dead space) 50 b betweenspacer elements 50 as fluid is delivered from the pump chamber 181. Forexample, if the spacer elements 50 were arranged in the stadium seatingarrangement shown in FIG. 6 without breaks (or aisles) 50 a or othermeans of allowing liquid and air to flow between spacer elements 50, themembrane 15 might bottom out on the spacer element 50 located at theoutermost periphery of the pump chamber 181, trapping whatever gas orliquid is present in the void between this outermost spacer element 50and the side portions 181 a of the pump chamber wall. Similarly, if themembrane 15 bottomed out on any two adjacent spacer elements 50, any gasand liquid in the void between the elements 50 may become trapped. Insuch an arrangement, at the end of the pump stroke, air or other gas atthe center of pump chamber 181 could be delivered while liquid remainsin the outer rows. Supplying breaks (or aisles) 50 a or other means offluidic communication between the voids between spacer elements 50 helpsto maintain an equal gas level throughout the voids during the pumpstroke, such that air or other gas may be inhibited from leaving thepump chamber 181 unless the liquid volume has been substantiallydelivered.

In certain embodiments, spacer elements 50 and/or the membrane 15 may bearranged so that the membrane 15 generally does not wrap or otherwisedeform around individual spacers 50 when pressed into contact with them,or otherwise extend significantly into the voids between spacers 50.Such an arrangement may lessen any stretching or damage to membrane 15caused by wrapping or otherwise deforming around one or more individualspacer elements 50. For example, it has also been found to beadvantageous in this embodiment to make the size of the voids betweenspacers 50 approximately equal in width to the width of the spacers 50.This feature has shown to help prevent deformation of the membrane 15,e.g., sagging of the membrane into the voids between spacers 50, whenthe membrane 15 is forced into contact with the spacers 50 during apumping operation.

In accordance with another aspect of the invention, the inner wall ofpump chambers 181 may define a depression that is larger than the space,for example a semi-elliptical or domed space, intended to be swept bythe pump chamber portion 151 of the membrane 15. In such instances, oneor more spacer elements 50 may be positioned below the domed regionintended to be swept by the membrane portion 151 rather than extendinginto that domed region. In certain instances, the ends of spacerelements 50 may define the periphery of the domed region intended to beswept by the membrane 15. Positioning spacer elements 50 outside of, oradjacent to, the periphery of the domed region intended to be swept bythe membrane portion 151 may have a number of advantages. For example,positioning one or more spacer elements 50 such that the spacer elementsare outside of, or adjacent to, the domed region intended to be swept bythe flexible membrane provides a dead space between the spacers and themembrane, such as described above, while minimizing any reduction to theintended stroke capacity of pump chambers 181.

It should be understood that the spacer elements 50, if present, in apump chamber may be arranged in any other suitable way, such as forexample, shown in FIG. 7. The left side pump chamber 181 in FIG. 7includes spacers 50 arranged similarly to that in FIG. 6, but there isonly one break or aisle 50 a that runs vertically through theapproximate center of the pump chamber 181. The spacers 50 may bearranged to define a concave shape similar to that in FIG. 6 (i.e., thetops of the spacers 50 may form the semi-elliptical shape shown in FIGS.3 and 4), or may be arranged in other suitable ways, such as to form aspherical shape, a box-like shape, and so on. The right-side pumpchamber 181 in FIG. 7 shows an embodiment in which the spacers 50 arearranged vertically with voids 50 b between spacers 50 also arrangedvertically. As with the left-side pump chamber, the spacers 50 in theright-side pump chamber 181 may define a semi-elliptical, spherical,box-like or any other suitably shaped depression. It should beunderstood, however, that the spacer elements 50 may have a fixedheight, a different spatial pattern that those shown, and so on.

Also, the membrane 15 may itself have spacer elements or other features,such as ribs, bumps, tabs, grooves, channels, etc., in addition to, orin place of the spacer elements 50. Such features on the membrane 15 mayhelp prevent sticking of the membrane 15, etc., and/or provide otherfeatures, such as helping to control how the sheet folds or otherwisedeforms when moving during pumping action. For example, bumps or otherfeatures on the membrane 15 may help the sheet to deform consistentlyand avoid folding at the same area(s) during repeated cycles. Folding ofa same area of the membrane 15 at repeated cycles may cause the membrane15 to prematurely fail at the fold area, and thus features on themembrane 15 may help control the way in which folds occur and where.

In this illustrative embodiment, the base member 18 of the cassette 24defines a plurality of controllable valve features, fluid pathways andother structures to guide the movement of fluid in the cassette 24. FIG.6 shows a plan view of the pump chamber side of the base member 18,which is also seen in perspective view in FIG. 3. FIG. 8 shows aperspective view of a back side of the base member 18, and FIG. 9 showsa plan view of the back side of the base member 18. The tube 156 foreach of the ports 150, 152 and 154 fluidly communicates with arespective valve well 183 that is formed in the base member 18. Thevalve wells 183 are fluidly isolated from each other by wallssurrounding each valve well 183 and by sealing engagement of themembrane 15 with the walls around the wells 183. As mentioned above, themembrane 15 may sealingly engage the walls around each valve well 183(and other walls of the base member 18) by being pressed into contactwith the walls, e.g., when loaded into the cycler 14. Fluid in the valvewells 183 may flow into a respective valve port 184, if the membrane 15is not pressed into sealing engagement with the valve port 184. Thus,each valve port 184 defines a valve (e.g., a “volcano valve”) that canbe opened and closed by selectively moving a portion of the membrane 15associated with the valve port 184. As will be described in more detailbelow, the cycler 14 may selectively control the position of portions ofthe membrane 15 so that valve ports (such as ports 184) may be opened orclosed so as to control flow through the various fluid channels andother pathways in the cassette 24. Flow through the valve ports 184leads to the back side of the base member 18. For the valve ports 184associated with the heater bag and the drain (ports 150 and 152), thevalve ports 184 lead to a common channel 200 formed at the back side ofthe base member 18. As with the valve wells 183, the channel 200 isisolated from other channels and pathways of the cassette 24 by thesheet 16 making sealing contact with the walls of the base member 18that form the channel 200. For the valve port 184 associated with thepatient line port 154, flow through the port 184 leads to a commonchannel 202 on the back side of the base member 18.

Returning to FIG. 6, each of the spikes 160 (shown uncapped in FIG. 6)fluidly communicates with a respective valve well 185, which areisolated from each other by walls and sealing engagement of the membrane15 with the walls that form the wells 185. Fluid in the valve wells 185may flow into a respective valve port 186, if the membrane 15 is not insealing engagement with the port 186. (Again, the position of portionsof the membrane 15 over each valve port 186 can be controlled by thecycler 14 to open and close the valve ports 186.) Flow through the valveports 186 leads to the back side of the base member 18 and into thecommon channel 202. Thus, in accordance with one aspect of theinvention, a cassette may have a plurality of solution supply lines (orother lines that provide materials for providing dialysate) that areconnected to a common manifold or channel of the cassette, and each linemay have a corresponding valve to control flow from/to the line withrespect to the common manifold or channel. Fluid in the channel 202 mayflow into lower openings 187 of the pump chambers 181 by way of openings188 that lead to lower pump valve wells 189 (see FIG. 6). Flow from thelower pump valve wells 189 may pass through a respective lower pumpvalve port 190 if a respective portion of the membrane 15 is not pressedin sealing engagement with the port 190. As can be seen in FIG. 9, thelower pump valve ports 190 lead to a channel that communicates with thelower openings 187 of the pump chambers 181. Flow out of the pumpchambers 181 may pass through the upper openings 191 and into a channelthat communicates with an upper valve port 192. Flow from the uppervalve port 192 (if the membrane 15 is not in sealing engagement with theport 192) may pass into a respective upper valve well 194 and into anopening 193 that communicates with the common channel 200 on the backside of the base member 18.

As will be appreciated, the cassette 24 may be controlled so that thepump chambers 181 can pump fluid from and/or into any of the ports 150,152 and 154 and/or any of the spikes 160. For example, fresh dialysateprovided by one of the containers 20 that is connected by a line 30 toone of the spikes 160 may be drawn into the common channel 202 byopening the appropriate valve port 186 for the proper spike 160 (andpossibly closing other valve ports 186 for other spikes). Also, thelower pump valve ports 190 may be opened and the upper pump valve ports192 may be closed. Thereafter, the portion of the membrane 15 associatedwith the pump chambers 181 (i.e., pump membranes 151) may be moved(e.g., away from the base member 18 and the pump chamber inner wall) soas to lower the pressure in the pump chambers 181, thereby drawing fluidin through the selected spike 160 through the corresponding valve port186, into the common channel 202, through the openings 188 and into thelower pump valve wells 189, through the (open) lower pump valve ports190 and into the pump chambers 181 through the lower openings 187. Thevalve ports 186 are independently operable, allowing for the option todraw fluid through any one or a combination of spikes 160 and associatedsource containers 20, in any desired sequence, or simultaneously. (Ofcourse, only one pump chamber 181 need be operable to draw fluid intoitself. The other pump chamber may be left inoperable and closed off toflow by closing the appropriate lower pump valve port 190.)

With fluid in the pump chambers 181, the lower pump valve ports 190 maybe closed, and the upper pump valve ports 192 opened. When the membrane15 is moved toward the base member 18, the pressure in the pump chambers181 may rise, causing fluid in the pump chambers 181 to pass through theupper openings 191, through the (open) upper pump valve ports 192 andinto the upper pump valve wells 194, through the openings 193 and intothe common channel 200. Fluid in the channel 200 may be routed to theheater bag port 150 and/or the drain port 152 (and into thecorresponding heater bag line or drain line) by opening the appropriatevalve port 184. In this way, for example, fluid in one or more of thecontainers 20 may be drawn into the cassette 24, and pumped out to theheater bag 22 and/or the drain.

Fluid in the heater bag 22 (e.g., after having been suitably heated onthe heater tray for introduction into the patient) may be drawn into thecassette 24 by opening the valve port 184 for the heater bag port 150,closing the lower pump valve ports 190, and opening the upper pump valveports 192. By moving the portions of the membrane 15 associated with thepump chambers 181 away from the base member 18, the pressure in the pumpchambers 181 may be lowered, causing fluid flow from the heater bag 22and into the pump chambers 181. With the pump chambers 181 filled withheated fluid from the heater bag 22, the upper pump valve ports 192 maybe closed and the lower pump valve ports 190 opened. To route the heateddialysate to the patient, the valve port 184 for the patient port 154may be opened and valve ports 186 for the spikes 160 closed. Movement ofthe membrane 15 in the pump chambers 181 toward the base member 18 mayraise the pressure in the pump chambers 181 causing fluid to flowthrough the lower pump valve ports 190, through the openings 188 andinto the common channel 202 to, and through, the (open) valve port 184for the patient port 154. This operation may be repeated a suitablenumber of times to transfer a desired volume of heated dialysate to thepatient.

When draining the patient, the valve port 184 for the patient port 154may be opened, the upper pump valve ports 192 closed, and the lower pumpvalve ports 190 opened (with the spike valve ports 186 closed). Themembrane 15 may be moved to draw fluid from the patient port 154 andinto the pump chambers 181. Thereafter, the lower pump valve ports 190may be closed, the upper valve ports 192 opened, and the valve port 184for the drain port 152 opened. Fluid from the pump chambers 181 may thenbe pumped into the drain line for disposal or for sampling into a drainor collection container. (Alternatively, fluid may also be routed to oneor more spikes 160/lines 30 for sampling or drain purposes). Thisoperation may be repeated until sufficient dialysate is removed from thepatient and pumped to the drain.

The heater bag 22 may also serve as a mixing container. Depending on thespecific treatment requirements for an individual patient, dialysate orother solutions having different compositions can be connected to thecassette 24 via suitable solution lines 30 and spikes 160. Measuredquantities of each solution can be added to heater bag 22 using cassette24, and admixed according to one or more pre-determined formulae storedin microprocessor memory and accessible by control system 16.Alternatively, specific treatment parameters can be entered by the uservia user interface 144. The control system 16 can be programmed tocompute the proper admixture requirements based on the type of dialysateor solution containers connected to spikes 160, and can then control theadmixture and delivery of the prescribed mixture to the patient.

In accordance with an aspect of the invention, the pressure applied bythe pumps to dialysate that is infused into the patient or removed fromthe patient may be controlled so that patient sensations of “tugging” or“pulling” resulting from pressure variations during drain and filloperations may be minimized. For example, when draining dialysate, thesuction pressure (or vacuum/negative pressure) may be reduced near theend of the drain process, thereby minimizing patient sensation ofdialysate removal. A similar approach may be used when nearing the endof a fill operation, i.e., the delivery pressure (or positive pressure)may be reduced near the end of fill. Different pressure profiles may beused for different fill and/or drain cycles in case the patient is foundto be more or less sensitive to fluid movement during different cyclesof the therapy. For example, a relatively higher (or lower) pressure maybe used during fill and/or drain cycles when a patient is asleep, ascompared to when the patient is awake. The cycler 14 may detect thepatient's sleep/awake state, e.g., using an infrared motion detector andinferring sleep if patient motion is reduced, or using a detected changein blood pressure, brain waves, or other parameter that is indicative ofsleep, and so on. Alternately, the cycler 14 may simply “ask” thepatient—“are you asleep?” and control system operation based on thepatient's response (or lack of response).

Set Loading and Operation

FIG. 10 shows a perspective view of the APD system 10 of FIG. 1 with thedoor 141 of the cycler 14 lowered into an open position, exposing amounting location 145 for the cassette 24 and a carriage 146 for thesolution lines 30. (In this embodiment, the door 141 is mounted by ahinge at a lower part of the door 141 to the cycler housing 82.) Whenloading the set 12, the cassette 24 is placed in the mounting location145 with the membrane 15 and the pump chamber side of the cassette 24facing upwardly, allowing the portions of the membrane 15 associatedwith the pump chambers and the valve ports to interact with a controlsurface 148 of the cycler 14 when the door 141 is closed. The mountinglocation 145 may be shaped so as to match the shape of the base member18, thereby ensuring proper orientation of the cassette 24 in themounting location 145. In this illustrative embodiment, the cassette 24and mounting location 145 have a generally rectangular shape with asingle larger radius corner which requires the user to place thecassette 24 in a proper orientation into the mounting location 145 orthe door 141 will not close. It should be understood, however, thatother shapes or orientation features for the cassette 24 and/or themounting location 145 are possible.

In accordance with an aspect of the invention, when the cassette 24 isplaced in the mounting location 145, the patient, drain and heater baglines 34, 28 and 26 are routed through a channel 40 in the door 141 tothe left as shown in FIG. 10. The channel 40, which may include guides41 or other features, may hold the patient, drain and heater bag lines34, 28 and 26 so that an occluder 147 may selectively close/open thelines for flow. Upon closing of door 141, occluder 147 can compress oneor more of patient, drain and heater bag lines 34, 28 and 26 againstoccluder stop 29. Generally, the occluder 147 may allow flow through thelines 34, 28 and 26 when the cycler 14 is operating (and operatingproperly), yet occlude the lines when the cycler 14 is powered down(and/or not operating properly). (Occlusion of the lines may beperformed by pressing on the lines, or otherwise pinching the lines toclose off the flow path in the lines.) Preferably, the occluder 147 mayselectively occlude at least the patient and drain lines 34 and 28.

When the cassette 24 is mounted and the door 141 is closed, the pumpchamber side of the cassette 24 and the membrane 15 may be pressed intocontact with the control surface 148, e.g., by an air bladder, spring orother suitable arrangement in the door 141 behind the mounting location145 that squeezes the cassette 24 between the mounting location 145 andthe control surface 148. This containment of the cassette 24 may pressthe membranes 15 and 16 into contact with walls and other features ofthe base member 18, thereby isolating channels and other flow paths ofthe cassette 24 as desired. The control surface 148 may include aflexible gasket, e.g., a sheet of silicone rubber or other material,that is associated with the membrane 15 and can selectively moveportions of the membrane 15 to cause pumping action in the pump chambers181 and opening/closing of valve ports of the cassette 24. The controlsurface 148 may be associated with the various portions of the membrane15, e.g., placed into intimate contact with each other, so that portionsof the membrane 15 move in response to movement of correspondingportions of the control surface 148. For example, the membrane 15 andcontrol surface 148 may be positioned close together, and a suitablevacuum (or pressure that is lower relative to ambient) may be introducedthrough vacuum ports suitably located in the control surface 148, andmaintained, between the membrane 15 and the control surface 148 so thatthe membrane 15 and the control surface 148 are essentially stucktogether, at least in regions of the membrane 15 that require movementto open/close valve ports and/or to cause pumping action. In anotherembodiment, the membrane 15 and control surface 148 may be adheredtogether, or otherwise suitably associated.

Before closing the door 141 with the cassette 24 loaded, one or moresolution lines 30 may be loaded into the carriage 146. The end of eachsolution line 30 may include a cap 31 and a region 33 for labeling orattaching an indicator or identifier. The indicator, for example, can bean identification tag that snaps onto the tubing at indicator region 33.In accordance with an aspect of the invention and as will be discussedin more detail below, the carriage 146 and other components of thecycler 14 may be operated to remove the cap(s) 31 from lines 30,recognize the indicator for each line 30 (which may provide anindication as to the type of solution associated with the line, anamount of solution, etc.) and fluidly engage the lines 30 with arespective spike 160 of the cassette 24. This process may be done in anautomated way, e.g., after the door 141 is closed and the caps 31 andspikes 160 are enclosed in a space protected from human touch,potentially reducing the risk of contamination of the lines 30 and/orthe spikes 160 when connecting the two together. For example, uponclosing of the door 141, the indicator regions 33 may be assessed (e.g.,visually by a suitable imaging device and software-based imagerecognition, by RFID techniques, etc.) to identify what solutions areassociated with which lines 30. The aspect of the invention regardingthe ability to detect features of a line 30 by way of an indicator atindicator region 33 may provide benefits such as allowing a user toposition lines 30 in any location of the carriage 146 without having anaffect on system operation. That is, since the cycler 14 canautomatically detect solution line features, there is no need to ensurethat specific lines are positioned in particular locations on thecarriage 146 for the system to function properly. Instead, the cycler 14may identify which lines 30 are where, and control the cassette 24 andother system features appropriately. For example, one line 30 andconnected container may be intended to receive used dialysate, e.g., forlater testing. Since the cycler 14 can identify the presence of thesample supply line 30, the cycler 14 can route used dialysate to theappropriate spike 160 and line 30. As discussed above, since the spikes160 of the cassette 24 all feed into a common channel, the input fromany particular spike 160 can be routed in the cassette 24 in any desiredway by controlling valves and other cassette features.

With lines 30 mounted, the carriage 146 may be moved to the left asshown in FIG. 10 (again, while the door 141 is closed), positioning thecaps 31 over a respective spike cap 63 on a spike 160 of the cassette 24and adjacent a cap stripper 149. The cap stripper 149 may extendoutwardly (toward the door 141 from within a recess in the cycler 14housing) to engage the caps 31. (For example, the cap stripper 149 mayinclude five fork-shaped elements that engage with a correspondinggroove in the caps 31, allowing the cap stripper 149 to resistleft/right movement of the cap 31 relative to the cap stripper 149.) Byengaging the caps 31 with the cap stripper 149, the caps 31 may alsogrip the corresponding spike cap 63. Thereafter, with the caps 31engaged with corresponding spike caps 63, the carriage 146 and capstripper 149 may move to the right, removing the spike caps 63 from thespikes 160 that are engaged with a corresponding cap 31. (One possibleadvantage of this arrangement is that spike caps 63 are not removed inlocations where no solution line 30 is loaded because engagement of thecap 31 from a solution line 30 is required to remove a spike cap 63.Thus, if a solution line will not be connected to a spike 160, the capon the spike 160 is left in place.) The cap stripper 149 may then stoprightward movement (e.g., by contacting a stop), while the carriage 146continues movement to the right. As a result, the carriage 146 may pullthe terminal ends of the lines 30 from the caps 31, which remainattached to the cap stripper 149. With the caps 31 removed from thelines 30 (and the spike caps 63 still attached to the caps 31), the capstripper 149 may again retract with the caps 31 into the recess in thecycler 14 housing, clearing a path for movement of the carriage 146 andthe uncapped ends of the lines 30 toward the spikes 160. The carriage146 then moves left again, attaching the terminal ends of the lines 30with a respective spike 160 of the cassette 24. This connection may bemade by the spikes 160 piercing an otherwise closed end of the lines 30(e.g., the spikes may pierce a closed septum or wall in the terminalend), permitting fluid flow from the respective containers 20 to thecassette 24. In an embodiment, the wall or septum may be constructed ofa flexible and/or self-sealing material such as, for example, PVC,polypropylene, or silicone rubber.

In accordance with an aspect of the invention, the heater bag 22 may beplaced in the heater bag receiving section (e.g., a tray) 142, which isexposed by lifting a lid 143. (In this embodiment, the cycler 14includes a user or operator interface 144 that is pivotally mounted tothe housing 82, as discussed below. To allow the heater bag 22 to beplaced into the tray 142, the interface 144 may be pivoted upwardly outof the tray 142.) As is known in the art, the heater tray 142 may heatthe dialysate in the heater bag 22 to a suitable temperature, e.g., atemperature appropriate for introduction into the patient. In accordancewith an aspect of the invention, the lid 143 may be closed afterplacement of the heater bag 22 in the tray 142, e.g., to help trap heatto speed the heating process, and/or help prevent touching or othercontact with a relatively warm portion of the heater tray 142, such asits heating surfaces. In one embodiment, the lid 143 may be locked in aclosed position to prevent touching of heated portions of the tray 142,e.g., in the circumstance that portions of the tray 142 are heated totemperatures that may cause burning of the skin. Opening of the lid 143may be prevented, e.g., by a lock, until temperatures under the lid 143are suitably low.

In accordance with another aspect of the invention, the cycler 14includes a user or operator interface 144 that is pivotally mounted tothe cycler 14 housing and may be folded down into the heater tray 142.With the interface 144 folded down, the lid 143 may be closed to concealthe interface 144 and/or prevent contact with the interface 144. Theinterface 144 may be arranged to display information, e.g., in graphicalform, to a user, and receive input from the user, e.g., by using a touchscreen and graphical user interface. The interface 144 may include otherinput devices, such as buttons, dials, knobs, pointing devices, etc.With the set 12 connected, and containers 20 appropriately placed, theuser may interact with the interface 144 and cause the cycler 14 tostart a treatment and/or perform other functions.

However, prior to initiating a dialysis treatment cycle, the cycler 14must at least prime the cassette 24, the patient line 34, heater bag 22,etc., unless the set 12 is provided in a pre-primed condition (e.g., atthe manufacturing facility or otherwise before being put into use withthe cycler 14). Priming may be performed in a variety of ways, such ascontrolling the cassette 24 (namely the pumps and valves) to draw liquidfrom one or more solution containers 20 via a line 30 and pump theliquid through the various pathways of the cassette 24 so as to removeair from the cassette 24. Dialysate may be pumped into the heater bag22, e.g., for heating prior to delivery to the patient. Once thecassette 24 and heater bag line 26 are primed, the cycler 14 may nextprime the patient line 34. In one embodiment, the patient line 34 may beprimed by connecting the line 34 (e.g., by the connector 36) to asuitable port or other connection point on the cycler 14 and causing thecassette 24 to pump liquid into the patient line 34. The port orconnection point on the cycler 14 may be arranged to detect the arrivalof liquid at the end of the patient line (e.g., optically, by conductivesensor, or other), thus detecting that the patient line is primed. Asdiscussed above, different types of sets 12 may have differently sizedpatient lines 34, e.g., adult or pediatric size. In accordance with anaspect of the invention, the cycler 14 may detect the type of cassette24 (or at least the type of patient line 34) and control the cycler 14and cassette 24 accordingly. For example, the cycler 14 may determine avolume of liquid delivered by a pump in the cassette needed to prime thepatient line 34, and based on the volume, determine the size of thepatient line 34. Other techniques may be used, such as recognizing abarcode or other indicator on the cassette 24, patient line 34 or othercomponent that indicates the patient line type.

FIG. 11 shows a perspective view of the inner side of the door 141disconnected from the housing 82 of the cycler 14. This view moreclearly shows how the lines 30 are received in corresponding grooves inthe door 141 and the carriage 146 such that the indicator region 33 iscaptured in a specific slot of the carriage 146. With the indicator atindicator region 33 positioned appropriately when the tubing is mountedto the carriage 146, a reader or other device can identify indicia ofthe indicator, e.g., representing a type of solution in the container 20connected to the line 30, an amount of solution, a date of manufacture,an identity of the manufacturer, and so on. The carriage 146 is mountedon a pair of rails or guides 130 at top and bottom ends of the carriage146 (only the lower rail or guide 130 is shown in FIG. 11). Thus, thecarriage 146 can move left to right on the door 141 along the rails orguides 130. When moving toward the cassette mounting location 145 (tothe right in FIG. 11), the carriage 146 can move until it contacts stops131.

FIG. 12 shows a perspective view of a carriage drive assembly 132 in afirst embodiment that functions to move the carriage 146 to remove thecaps from spikes 160 on the cassette, remove caps 31 on the solutionlines 30 and connect lines 30 to the spikes 160. A drive element 133 isarranged to move left to right along rods 134. In this illustrativeembodiment, an air bladder powers the movement of the drive element 133along the rods 134, but any suitable drive mechanism may be used,including motors, hydraulic systems, etc. The drive element 133 hasforwardly extending tabs 135 that engage with corresponding slots 146aon the carriage 146 (see FIG. 11, which shows a top slot 146a on thecarriage 146). Engagement of the tabs 135 with the slots 146a allow thedrive element 133 to move the carriage 146 along the rails or guides130. The drive element 133 also includes a window 136, through which animaging device, such as a CCD or CMOS imager, may capture imageinformation of the indicators at indicator regions 33 on the lines 30mounted to the carriage 146. Image information regarding the indicatorsat indicator regions 33 may be provided from the imaging device to thecontrol system 16, which may obtain indicia, e.g., by image analysis.The drive element 133 can selectively move the cap stripper 149 both tothe left and right along the rods 134. The cap stripper 149 extendsforward and back using a separate drive mechanism, such as a pneumaticbladder.

FIG. 13 shows a left side perspective view of the carriage driveassembly 132, which more clearly shows how a stripper element of the capstripper 149 is arranged to move in and out (a direction generallyperpendicular to the rods 134) along grooves 149 a in the housing of thecap stripper 149. Each of the semicircular cut outs of the stripperelement may engage a corresponding groove of a cap 31 on a line 30 byextending forwardly when the cap 31 is appropriately positioned in frontof the stripper 149 by the drive element 133 and the carriage 146. Withthe stripper element engaged with the caps 31, the cap stripper 149 maymove with the carriage 146 as the drive element 133 moves. FIG. 14 showsa partial rear view of the carriage drive assembly 132. In thisembodiment, the drive element 133 is moved toward the cassette 24mounting location 145 by a first air bladder 137 which expands to forcethe drive element 133 to move to the right in FIG. 14. The drive elementcan be moved to the left by a second air bladder 138. Alternatively,drive element 133 can be moved back and forth by means of one or moremotors coupled to a linear drive gear assembly, such as a ball screwassembly (in which the carriage drive assembly is attached to a ballnut), or a rack and pinion assembly, for example. The stripper element1491 of the cap stripper 149 can be moved in and out of the cap stripperhousing by a third bladder, or alternatively, by a motor coupled to alinear drive assembly, as described previously.

FIGS. 15-18 show another embodiment of a carriage drive assembly 132 andcap stripper 149. As can be seen in the rear view of the carriage driveassembly 132 in FIG. 15, in this embodiment the drive element 133 ismoved right and left by a screw drive mechanism 1321. As can be seen inthe right rear perspective view of the carriage drive assembly 132 inFIG. 16, the stripper element is moved outwardly and inwardly by an airbladder 139, although other arrangements are possible as describedabove.

FIGS. 17 and 18 show left and right front perspective views of anotherembodiment for the stripper element 1491 of the cap stripper 149. Thestripper element 1491 in the embodiment shown in FIG. 13 included onlyfork-shaped elements arranged to engage with a cap 31 of a solution line30. In the FIGS. 17 and 18 embodiment, the stripper element 1491 notonly includes the fork-shaped elements 60, but also rocker arms 61 thatare pivotally mounted to the stripper element 1491. As will be explainedin more detail below, the rocker arms 61 assist in removing spike caps63 from the cassette 24. Each of the rocker arms 61 includes a solutionline cap engagement portion 61 a and a spike cap engagement portion 61b. The rocker arms 61 are normally biased to move so that the spike capengagement portions 61 b are positioned near the stripper element 1491,as shown in the rocker arms 61 in FIG. 18. However, when a cap 31 isreceived by a corresponding fork-shaped element 60, the solution linecap engagement portion 61 a contacts the cap 31, which causes the rockerarm 61 to pivot so that the spike cap engagement portion 61 b moves awayfrom the stripper element 1491, as shown in FIG. 17. This positionenables the spike cap engagement portion 61 b to contact a spike cap 63,specifically a flange on the spike cap 63.

FIG. 19 shows a front view of the stripper element 1491 and the locationof several cross-sectional views shown in FIGS. 20-22. FIG. 20 shows therocker arm 61 with no spike cap 63 or solution line cap 31 positionednear the stripper element 1491. The rocker arm 61 is pivotally mountedto the stripper element 1491 at a point approximately midway between thespike cap engagement portion 61 b and the solution cap engagementportion 61 a. As mentioned above, the rocker arm 61 is normally biasedto rotate in a counterclockwise direction as shown in FIG. 20 so thatthe spike cap engagement portion 61 b is positioned near the stripperelement 1491. FIG. 21 shows that the rocker arm 61 maintains thisposition (i.e., with the spike cap engagement portion 61 b located nearthe stripper element 1491) even when the stripper element 1491 advancestoward a spike cap 63 in the absence of a solution line cap 31 engagingwith the fork-shaped element 60. As a result, the rocker arm 61 will notrotate clockwise or engage the spike cap 63 unless a solution line cap31 is present. Thus, a spike cap 63 that does not engage with a solutionline cap 31 will not be removed from the cassette 24.

FIG. 22 shows an example in which a solution line cap 31 is engaged withthe fork-shaped element 60 and contacts the solution line cap engagementportion 61 a of the rocker arm 61. This causes the rocker arm 61 torotate in a clockwise direction (as shown in the figure) and the spikecap engagement portion 61 b to engage with the spike cap 63. In thisembodiment, engagement of the portion 61 b includes positioning theportion 61 b adjacent a second flange 63 a on the spike cap 63 so thatwhen the stripper element 1491 moves to the right (as shown in FIG. 22),the spike cap engagement portion 61 b will contact the second flange 63a and help pull the spike cap 63 from the corresponding spike 160. Notethat the solution line cap 31 is made of a flexible material, such assilicone rubber, to allow a barb 63 c of the spike cap 63 to stretch thehole 31 b of cap 31 (see FIG. 23) and be captured by a circumferentialinner groove or recess within cap 31. A first flange 63 b on the spikecap 63 acts as a stop for the end of solution line cap 31. The wallsdefining the groove or recess in the cap 31 hole 31 b may besymmetrical, or preferably asymmetrically arranged to conform to theshape of the barb 63 c. (See FIG. 33 for a cross sectional view of thecap 31 and the groove or recess.) The second flange 63 a on spike cap 63acts as a tooth with which the spike cap engagement portion 61 b of therocker arm 61 engages in order to provide an additional pulling force todisengage the spike cap 63 from the spike 160, if necessary.

FIG. 23 shows a close-up exploded view of the connector end 30 a of asolution line 30 with the cap 31 removed. (In FIG. 23, the caps 31 areshown without a finger pull ring like that shown in FIG. 24 for clarity.A pull ring need not be present for operation of the cap 31 with thecycler 14. It may be useful, however, in allowing an operator tomanually remove the cap 31 from the terminal end of solution line 30, ifnecessary). In this illustrative embodiment, the indicator at indicatorregion 33 has an annular shape that is sized and configured to fitwithin a corresponding slot of the carriage 146 when mounted as shown inFIGS. 10 and 11. Of course, the indicator may take any suitable form.The cap 31 is arranged to fit over the extreme distal end of theconnector end 30 a, which has an internal bore, seals, and/or otherfeatures to enable a leak-free connection with a spike 160 on a cassette24. The connector end 30 a may include a pierceable wall or septum (notshown—see FIG. 33 item 30 b) that prevents leakage of solution in theline 30 from the connector end 30 a, even if the cap 31 is removed. Thewall or septum may be pierced by the spike 160 when the connector end 30a is attached to the cassette 24, allowing flow from the line 30 to thecassette 24. As discussed above, the cap 31 may include a groove 31 athat is engaged by a fork-shaped element 60 of the cap stripper 149. Thecap 31 may also include a hole 31 b that is arranged to receive a spikecap 63. The hole 31 b and the cap 31 may be arranged so that, with thecap stripper 149 engaged with the groove 31 a and the spike cap 63 of aspike 160 received in the hole 31 b, the cap 31 may grip the spike cap63 suitably so that when the carriage 146/cap stripper 149 pulls the cap31 away from the cassette 24, the spike cap 63 is removed from the spike160 and is carried by the cap 31. This removal may be assisted by therocker arm 61 engaging with the second flange 63 a or other feature onthe spike cap 63, as described above. Thereafter, the cap 31 and spikecap 63 may be removed from the connector end 30 a and the line 30attached to the spike 160 by the carriage 146.

Once treatment is complete, or the line 30 and/or the cassette 24 areready for removal from cycler 14, the cap 31 and attached spike cap 63may be re-mounted on the spike 160 and the line 30 before the door 141is permitted to be opened and the cassette 24 and line 30 removed fromthe cycler 14. Alternatively, the cassette 24 and solution containerswith lines 30 can be removed en bloc from cycler 14 without re-mountingcap 31 and the attached spike cap 63. An advantage of this approachincludes a simplified removal process, and avoidance of any possiblefluid leaks onto the cycler or surrounding area from improperlyre-mounted or inadequately sealing caps.

FIGS. 24-32 show a perspective view of the carriage 146, cap stripper149 and cassette 24 during a line mounting and automatic connectionoperation. The door 141 and other cycler components are not shown forclarity. In FIG. 24, the carriage 146 is shown in a folded downposition, as if the door 141 is open in the position shown in FIG. 8.The lines 30 and cassette 24 are positioned to be lowered onto the door141. In FIG. 25, the lines 30 are loaded into the carriage 146 and thecassette 24 is loaded into the mounting location 145. At this point thedoor 141 can be closed to ready the cycler for operation. In FIG. 26,the door 141 is closed. Identifiers or indicators located at indicatorregion 33 on the lines 30 may be read to identify various linecharacteristics so that the cycler 14 can determine what solutions, howmuch solution, etc., are loaded. In FIG. 27, the carriage 146 has movedto the left, engaging the caps 31 on the lines 30 with correspondingspike caps 63 on the cassette 24. During the motion, the drive element133 engages the cap tripper 149 and moves the cap stripper 149 to theleft as well. However, the cap stripper 149 remains in a retractedposition. In FIG. 28, the cap stripper 149 moves forward to engage thefork-shaped elements 60 with the caps 31, thereby engaging the caps 31that have been coupled to the spike caps 63. If present, the rocker arms61 may move to an engagement position with respect to the spike caps 63.Next, as shown in FIG. 29, the carriage 146 and the cap stripper 149move to the right, away from the cassette 24 so as to pull the caps 31and spike caps 63 from the corresponding spikes 160 on the cassette 24.It is during this motion that the rocker arms 61, if present, may assistin pulling spike caps 63 from the cassette 24. In FIG. 30, the capstripper 149 has stopped its movement to the right, while the carriage146 continues to move away from the cassette 24. This causes theconnector ends 30 a of the lines 30 to be pulled from the caps 31,leaving the caps 31 and spike caps 63 mounted on the cap stripper 149 byway of the fork-shaped elements 60. In FIG. 31, the cap stripper 149retracts, clearing a path for the carriage 146 to move again toward thecassette 24. In FIG. 32, the carriage 146 moves toward the cassette 24to engage the connector ends 30 a of the lines 30 with the correspondingspikes 160 of the cassette 24. The carriage 146 may remain in thisposition during cycler operation. Once treatment is complete, themovements shown in FIGS. 24-32 may be reversed to recap the spikes 160and the solution lines 30 and remove the cassette 24 and/or lines 30from the cycler 14.

To further illustrate the removal of caps 31 and spike caps 63, FIG. 33shows a cross-sectional view of the cassette 24 at five different stagesof line 30 connection. At the top spike 160, the spike cap 63 is stillin place on the spike 160 and the solution line 30 is positioned awayfrom the cassette 24, as in FIG. 26. At the second spike 160 down fromthe top, the solution line 30 and cap 31 are engaged over the spike cap63, as in FIGS. 27 and 28. At this point, the cap stripper 149 mayengage the cap 31 and spike cap 63. At the third spike 160 from the top,the solution line 30, cap 31 and spike cap 63 have moved away from thecassette 24, as in FIG. 29. At this point, the cap stripper 149 may stopmovement to the right. At the fourth spike 160 from the top, thesolution line 30 continues movement to the right, removing the cap 31from the line 30, as in FIG. 30. Once the caps 31 and 63 are retracted,the solution line 30 moves to the left to fluidly connect the connectorend 30 a of the line 30 to the spike 160, as in FIG. 32.

Various sensors can be used to help verify that the carriage 146 and capstripper 149 move fully to their expected positions. In an embodiment,the carriage drive assembly 132 can be equipped with six Hall effectsensors (not shown): four for the carriage 146 and two for the capstripper 149. A first cap stripper sensor may be located to detect whenthe cap stripper 149 is fully retracted. A second cap stripper sensormay be located to detect when the cap stripper 149 is fully extended. Afirst carriage sensor may be located to detect when the carriage 146 isin the “home” position, i.e. in position to permit loading the cassette24 and lines 30. A second carriage sensor may be located to detect whenthe carriage 146 is in position to have engaged the spike caps 63. Athird carriage sensor may be located to detect when the carriage 146 hasreached a position to have removed the caps 31 from the lines 30. Afourth carriage sensor may be located to detect when the carriage 146has moved to a position to have engaged the connector ends 30 a of thelines 30 with the corresponding spikes 160 of the cassette 24. In otherembodiments, a single sensor can be used to detect more than one of thecarriage positions described above. The cap stripper and carriagesensors can provide input signals to an electronic control board(“autoconnect board”), which in turn can communicate specificconfirmation or error codes to the user via the user interface 144.

There may be an advantage in adjusting the force with which the carriage146 engages the spike caps 63, depending on how many lines 30 are beinginstalled. The force required to complete a connection to the cassette24 increases with the number of caps 31 that must be coupled to spikecaps 63. The sensing device for detecting and reading information fromthe line indicators at indicator regions 33 can also be used to providethe data required to adjust the force applied to drive element 133. Theforce can be generated by a number of devices, including, for example,the first air bladder 137, or a linear actuator such as a motor/ballscrew. An electronic control board (such as, for example, theautoconnect board) can be programmed to receive input from the linedetection sensor(s), and send an appropriate control signal either tothe motor of a linear actuator, or to the pneumatic valve that controlsinflation of air bladder 137. The controller 16 can control the degreeor rate of movement of drive element 133, for example by modulating thevoltage applied to the motor of a linear actuator, or by modulating thepneumatic valve controlling the inflation of bladder 137.

The aspect of the invention by which caps 31 on lines 30 are removedtogether with caps 63 on spikes 160 of the cassette 24 may provide otheradvantages aside from simplicity of operation. For example, since spikecaps 63 are removed by way of their engagement with a cap 31 on a line30, if there is no line 30 mounted at a particular slot on the carriage146, the spike cap 63 at that position will not be removed. For example,although the cassette 24 includes five spikes 160 and correspondingspike caps 63, the cycler 14 can operate with four or less (even no)lines 30 associated with the cycler 14. For those slots on the carriage146 where no line 30 is present, there will be no cap 31, and thus nomechanism by which a spike cap 63 at that position can be removed. Thus,if no line 30 will be connected to a particular spike 160, the cap 63 onthat spike 160 may remain in place during use of the cassette 24. Thismay help prevent leakage at the spike 160 and/or contamination at thespike 160.

The cassette 24 in FIG. 33 includes a few features that are differentfrom those shown, for example, in the embodiment shown in FIGS. 3, 4 and6. In the FIGS. 3, 4 and 6 embodiment, the heater bag port 150, drainline port 152 and patient line port 154 are arranged to have a centraltube 156 and a skirt 158. However, as mentioned above and shown in FIG.33, the ports 150, 152, 154 may include only the central tube 156 and noskirt 158. This is also shown in FIG. 34. The embodiment depicted inFIG. 34 includes raised ribs formed on the outside surface of theleft-side pump chamber 181. The raised ribs may also be provided on theright-side pump chamber 181, and may provide additional contact pointsof the outside walls of pump chambers 181 with the mechanism in the door141 at the cassette mounting location 145, which presses the cassetteagainst the control surface 148 when the door 141 is closed. The raisedribs are not required, and instead the pump chambers 181 may have no ribor other features, as shown for the right-side pump chamber 181 in FIG.34. Similarly, the spikes 160 in the FIGS. 3, 4 and 6 embodiment includeno skirt or similar feature at the base of the spike 160, whereas theembodiment in FIG. 33 includes a skirt 160 a. This is also shown in FIG.34. The skirt 160 a may be arranged to receive the end of the spike cap63 in a recess between the skirt 160 a and the spike 160, helping toform a seal between the spike 160 and the spike cap 63.

Another inventive feature shown in FIG. 33 relates to the arrangement ofthe distal tip of the spike 163 and the lumen 159 through the spike 160.In this aspect, the distal tip of the spike 160 is positioned at or nearthe longitudinal axis of the spike 160, which runs generally along thegeometric center of the spike 160. Positioning the distal tip of thespike 160 at or near the longitudinal axis may help ease alignmenttolerances when engaging the spike 160 with a corresponding solutionline 30 and help the spike 160 puncture a septum or membrane 30 b in theconnector end 30 a of the line 30. As a result, the lumen 159 of thespike 160 is located generally off of the longitudinal axis of the spike160, e.g., near a bottom of the spike 160 as shown in FIG. 33 and asshown in an end view of a spike 160 in FIG. 35. Also, the distal end ofthe spike 160 has a somewhat reduced diameter as compared to moreproximal portions of the spike 160 (in this embodiment, the spike 160actually has a step change in diameter at about ⅔ of the length of thespike 160 from the body 18). The reduced diameter of the spike 160 atthe distal end may provide clearance between the spike 160 and the innerwall of the line 30, thus allowing the septum 30 b a space to fold backto be positioned between the spike 160 and the line 30 when pierced bythe spike 160. The stepped feature on the spike 160 may also be arrangedto engage the line 30 at the location where the septum 30 b is connectedto the inner wall of the line 30, thus enhancing a seal formed betweenthe line 30 and the spike 160.

Once the cassette 24 and lines 30 are loaded into the cycler 14, thecycler 14 must control the operation of the cassette 24 to move fluidfrom the solution lines 30 to the heater bag 22 and to the patient. FIG.36 shows a plan view of the control surface 148 of the cycler 14 thatinteracts with the pump chamber side of the cassette 24 (e.g., shown inFIG. 6) to cause fluid pumping and flowpath control in the cassette 24.When at rest, the control surface 148, which may be described as a typeof gasket, and comprise a sheet of silicone rubber, may be generallyflat. Valve control regions 1481 may (or may not) be defined in thecontrol surface 148, e.g., by a scoring, groove, rib or other feature inor on the sheet surface, and be arranged to be movable in a directiongenerally transverse to the plane of the sheet. By movinginwardly/outwardly, the valve control regions 1481 can move associatedportions of the membrane 15 on the cassette 24 so as to open and closerespective valve ports 184, 186, 190 and 192 of the cassette 24, andthus control flow in the cassette 24. Two larger regions, pump controlregions 1482, may likewise be movable so as to move associated shapedportions 151 of the membrane 15 that cooperate with the pump chambers181. Like the shaped portions 151 of the membrane 15, the pump controlregions 1482 may be shaped in a way to correspond to the shape of thepump chambers 181 when the control regions 1482 are extended into thepump chambers 181. In this way, the portion of the control sheet 148 atthe pump control regions 1482 need not necessarily be stretched orotherwise resiliently deformed during pumping operation.

Each of the regions 1481 and 1482 may have an associated vacuum orevacuation port 1483 that may be used to remove all or substantially allof any air or other fluid that may be present between the membrane 15 ofcassette 24, and the control surface 148 of cycler 14, e.g., after thecassette 24 is loaded into the cycler 14 and the door 141 closed. Thismay help ensure close contact of the membrane 15 with the controlregions 1481 and 1482, and help control the delivery of desired volumeswith pump operation and/or the open/closed state of the various valveports. Note that the vacuum ports 1482 are formed in locations where thecontrol surface 148 will not be pressed into contact with a wall orother relatively rigid feature of the cassette 24. For example, inaccordance with one aspect of the invention, one or both of the pumpchambers of the cassette may include a vacuum vent clearance regionformed adjacent the pump chamber. In this illustrative embodiment asshown in FIGS. 3 and 6, the base member 18 may include vacuum vent portclearance or extension features 182 (e.g., recessed areas that arefluidly connected to the pump chambers) adjacent and outside theoval-shaped depressions forming the pump chambers 181 to allow thevacuum vent port 1483 for the pump control region 1482 to remove any airor fluid from between membrane 15 and control surface 148 (e.g., due torupture of the membrane 15) without obstruction. The extension featuremay also be located within the perimeter of pump chamber 181. However,locating vent port feature 182 outside the perimeter of pump chamber 181may preserve more of the pumping chamber volume for pumping liquids,e.g., allows for the full footprint of pump chamber 181 to be used forpumping dialysate. Preferably, extension feature 182 is located in avertically lower position in relation to pump chamber 181, so that anyliquid that leaks between membrane 15 and control surface 148 is drawnout through vacuum port 1483 at the earliest opportunity. Similarly,vacuum ports 1483 associated with valves 1481 are preferably located ina vertically inferior position with respect to valves 1481.

The control regions 1481 and 1482 may be moved by controlling apneumatic pressure and/or volume on a side of the control surface 148opposite the cassette 24, e.g., on a back side of the rubber sheet thatforms the control surface 148. For example, as shown in FIG. 37, thecontrol surface 148 may be backed by a mating block 170 that has controlchambers 171 located in association with each control region 1481, 1482,and that are isolated from each other (or at least can be controlledindependently of each other if desired). The surface of mating block 170forms an interface with cassette 24 when cassette 24 is pressed intooperative association with control surface 148 backed by mating block170. The control chambers of mating block 170 are thus coupled tocomplementary valve or pumping chambers of cassette 24, sandwichingcontrol regions 1481 and 1482 of control surface 148 adjacent to matingblock 170, and the associated regions of membrane 15 (such as shapedportion 151) adjacent to cassette 24. Air or other control fluid may bemoved into or out of the control chambers 171 of mating block 170 forthe regions 1481, 1482, thereby moving the control regions 1481, 1482 asdesired to open/close valve ports of the cassette 24 and/or effectpumping action at the pump chambers 181. In one illustrative embodimentshown in FIG. 37, the control chambers 171 may be arranged ascylindrically-shaped regions backing each of the valve control regions1481 and a pair of elliptical voids backing the pump control regions1482. Fluid control ports may be provided for each control chamber 171so that the cycler 14 can control the volume of fluid and/or thepressure of fluid in each of the control chambers. For example, themating block 170 may be mated with a manifold 172 that includes variousports, channels, openings, voids and/or other features that communicatewith the control chambers 171 and allow suitable pneumaticpressure/vacuum to be applied to the control chambers 171. Although notshown, control of the pneumatic pressure/vacuum may be performed in anysuitable way, such as through the use of controllable valves, pumps,pressure sensors, accumulators, and so on. Of course, it should beunderstood that the control regions 1481, 1482 may be moved in otherways, such as by gravity-based systems, hydraulic systems, and/ormechanical systems (such as by linear motors, etc.), or by a combinationof systems including pneumatic, hydraulic, gravity-based and mechanicalsystems.

In accordance with an aspect of the invention, the vacuum ports 1483 maybe used to detect leaks in the membrane 15, e.g., a liquid sensor in aconduit or chamber connected to a vacuum port 1483 may detect liquid ifthe membrane 15 is perforated or liquid otherwise is introduced betweenthe membrane 15 and the control surface 148. For example, vacuum ports1483 may align with and be sealingly associated with complementaryvacuum ports 173 in mating block 170, which in turn may be sealinglyassociated with fluid passages 1721 leading to a common fluid collectionchamber 1722 in manifold 172. The fluid collection chamber 1722 maycontain an inlet through which vacuum can be applied and distributed toall vacuum ports 1483 of control surface 148. By applying vacuum to thefluid collection chamber 1722, fluid may be drawn from each of thevacuum ports 173 and 1483, thus removing fluid from any space betweenthe membrane 15 and the control surface 148 at the various controlregions. However, if there is liquid present at one or more of theregions, the associated vacuum port 1483 may draw the liquid into thevacuum ports 173 and into the lines 1721 leading to the fluid collectionchamber 1722. Any such liquid may collect in the fluid collectionchamber 1722, and be detected by one or more suitable sensors, e.g., apair of conductivity sensors that detect a change in conductivity in thechamber 1722 indicating the presence of liquid. In this embodiment, thesensors may be located at a bottom side of the fluid collection chamber1722, while a vacuum source connects to the chamber 1722 at an upper endof the chamber 1722. Therefore, if liquid is drawn into the fluidcollection chamber 1722, the liquid may be detected before the liquidlevel reaches the vacuum source. Optionally, a hydrophobic filter, valveor other component may be place at the vacuum source connection pointinto the chamber 1722 to help further resist the entry of liquid intothe vacuum source. In this way, a liquid leak may be detected and actedupon by controller 16 (e.g., generating an alert, closing liquid inletvalves and ceasing pumping operations) before the vacuum source valve isplaced at risk of being contaminated by the liquid.

In one embodiment, the inner wall of the control chambers 171 caninclude raised elements somewhat analogous to the spacer elements 50 ofthe pump chamber, e.g., as shown in FIG. 37 for the control chambers 171associated with the pump control regions 1482. These raised elements cantake the form of plateau features, ribs, or other protrusions that keepthe control ports recessed away from the fully retracted control regions1482. This arrangement may allow for a more uniform distribution ofpressure or vacuum in the control chamber 171, and prevent prematureblocking of any control port by the control surface 148. A pre-formedcontrol surface 148 (at least in the pump control regions) may not beunder a significant stretching force when fully extended against eitherthe inner wall of the pump chamber of the cassette 24 during a deliverystroke, or the inner wall of the control chamber 171 during a fillstroke. It may therefore be possible for the control region 1482 toextend asymmetrically into the control chamber 171, causing the controlregion 1482 to prematurely close off one or more ports of the controlchamber before the chamber is fully evacuated. Having features on theinner surface of the control chamber 171 that prevent contact betweenthe control region 1482 and the control ports may help to assure thatthe control region 1482 can make uniform contact with the controlchamber inner wall during a fill stroke.

As suggested above, the cycler 14 may include a control system 16 with adata processor in electrical communication with the various valves,pressure sensors, motors, etc., of the system and is preferablyconfigured to control such components according to a desired operatingsequence or protocol. The control system 16 may include appropriatecircuitry, programming, computer memory, electrical connections, and/orother components to perform a specified task. The system may includepumps, tanks, manifolds, valves or other components to generate desiredair or other fluid pressure (whether positive pressure—above atmosphericpressure or some other reference—or negative pressure or vacuum—belowatmospheric pressure or some other reference) to control operation ofthe regions of the control surface 148, and other pneumatically-operatedcomponents. Further details regarding the control system 16 (or at leastportions of it) are provided below.

In one illustrative embodiment, the pressure in the pump controlchambers 171 may be controlled by a binary valve, e.g., which opens toexpose the control chamber 171 to a suitable pressure/vacuum and closesto cut off the pressure/vacuum source. The binary valve may becontrolled using a saw tooth-shaped control signal which may bemodulated to control pressure in the pump control chamber 171. Forexample, during a pump delivery stroke (i.e., in which positive pressureis introduced into the pump control chamber 171 to move the membrane15/control surface 148 and force liquid out of the pump chamber 181),the binary valve may be driven by the saw tooth signal so as to open andclose at a relatively rapid rate to establish a suitable pressure in thecontrol chamber 171 (e.g., a pressure between about 70-90 mmHg). If thepressure in the control chamber 171 rises above about 90 mmHg, the sawtooth signal may be adjusted to close the binary valve for a moreextended period. If the pressure drops below about 70 mmHg in thecontrol chamber 171, the saw tooth control signal may again be appliedto the binary valve to raise the pressure in the control chamber 171.Thus, during a typical pump operation, the binary valve will be openedand closed multiple times, and may be closed for one or more extendedperiods, so that the pressure at which the liquid is forced from thepump chamber 181 is maintained at a desired level or range (e.g., about70-90 mmHg).

In some embodiments and in accordance with an aspect of the invention,it may be useful to detect an “end of stroke” of the membrane 15/pumpcontrol region 1482, e.g., when the membrane 15 contacts the spacers 50in the pump chamber 181 or the pump control region 1482 contacts thewall of the pump control chamber 171. For example, during a pumpingoperation, detection of the “end of stroke” may indicate that themembrane 15/pump control region 1482 movement should be reversed toinitiate a new pump cycle (to fill the pump chamber 181 or drive fluidfrom the pump chamber 181). In one illustrative embodiment in which thepressure in the control chamber 171 for a pump is controlled by a binaryvalve driven by a saw tooth control signal, the pressure in the pumpchamber 181 will fluctuate at a relatively high frequency, e.g., afrequency at or near the frequency at which the binary valve is openedand closed. A pressure sensor in the control chamber 171 may detect thisfluctuation, which generally has a higher amplitude when the membrane15/pump control region 1482 are not in contact with the inner wall ofthe pump chamber 181 or the wall of the pump control chamber 171.However, once the membrane 15/pump control region 1482 contacts theinner wall of the pump chamber 181 or the wall of the pump controlchamber 171 (i.e., the “end of stroke”), the pressure fluctuation isgenerally damped or otherwise changes in a way that is detectable by thepressure sensor in the pump control chamber 171. This change in pressurefluctuation can be used to identify the end of stroke, and the pump andother components of the cassette 24 and/or cycler 14 may be controlledaccordingly.

Occluder

In one aspect of the invention, an occluder for opening/closing one ormore flexible lines may include a pair of opposed occluding members,which may be configured as resilient elements, such as flat plates madeof a spring steel (e.g., leaf springs), having a force actuatorconfigured to apply a force to one or both of the occluding members tooperate the occluder. In certain embodiments, the force actuator maycomprise an expandable or enlargable member positioned between theresilient elements. With the expandable member in a reduced sizecondition, the resilient elements may be in a flat or nearly flatcondition and urge a pinch head to engage with one or more lines so asto pinch the lines closed. However, when the expandable member urges theresilient elements apart, the resilient elements may bend and withdrawthe pinch head, releasing the lines and allowing flow through the lines.In other embodiments, the occluding members could be essentially rigidwith respect to the levels of force applied by the force actuator. Incertain embodiments, the force actuator may apply a force to one or bothopposed occluding members to increase the distance between the occludingmembers in at least a portion of the region where they are opposed toeffect opening or closing of the flexible tubing.

FIG. 38 shows an exploded view and FIG. 39 shows a partially assembledview of an illustrative embodiment of an occluder 147 that may be usedto close, or occlude, the patient and drain lines 34 and 28, and/orother lines in the cycler 14 or the set 12 (such as, for example, theheater bag line 26). The occluder 147 includes an optional pinch head161, e.g., a generally flat blade-like element that contacts the tubesto press the tubes against the door 141 and pinch the tubes closed. Inother embodiments, the function of the pinch head could be replaced byan extending edge of one or both of occluding members 165. The pinchhead 161 includes a gasket 162, such as an O-ring or other member, thatcooperates with the pinch head 161 to help resist entry of fluid (air orliquid for example) into the cycler 14 housing, e.g., in case of leakagein one of the occluded lines. The bellows gasket 162 is mounted to, andpinch head 161 passes through, a pinch head guide 163 that is mounted tothe front panel of the cycler housing, i.e., the panel exposed byopening the door 141. The pinch head guide 163 allows the pinch head 161to move in and out of the pinch head guide 163 without binding and/orsubstantial resistance to sliding motion of the pinch head 161. A pivotshaft 164 attaches a pair of opposed occluder members, comprising in theillustrated embodiment spring plates 165, that each include ahook-shaped pivot shaft bearing, e.g., like that found on standard doorhinges, to the pinch head 161. That is, the openings of shaft guides onthe pinch head 161, and the openings formed by the hook-shaped bearingson the spring plates 165 are aligned with each other and the pivot shaft164 is inserted through the openings so the pinch head 161 and thespring plates 165 are pivotally connected together. The spring plates165 may be made of any suitable material, such as steel, and may bearranged to be generally flat when unstressed. The opposite end of thespring plates 165 includes similar hook-shaped bearings, which arepivotally connected to a linear adjustor 167 by a second pivot shaft164. In this embodiment, the force actuator comprises a bladder 166 ispositioned between the spring plates 165 and arranged so that when fluid(e.g., air under pressure) is introduced into the bladder, the bladdermay expand and push the spring plates 165 away from each other in aregion between the pivot shafts 164. A linear adjustor 167 is fixed tothe cycler housing 82 while the pinch head 161 is allowed to float,although its movement is guided by the pinch head guide 163. The linearadjustor 167 includes slot holes at its lower end, allowing the entireassembly to be adjusted in position and thus permitting the pinch headto be appropriately positioned when the occluder 147 is installed in thecycler 14. A turnbuckle 168 or other arrangement may be used to helpadjust the position of the linear adjustor 167 relative to the housing82. That is, the pinch head 161 generally needs to be properlypositioned so that with the spring plates 165 located near each otherand the bladder 166 substantially emptied or at ambient pressure, thepinch head 161 suitably presses on the patient and drain lines so as topinch the tubes closed to flow without cutting, kinking or otherwisedamaging the tubes. The slot openings in the linear adjustor 167 allowsfor this fine positioning and fixing of the occluder 147 in place. Anoverride release device, such as provided by release blade 169 isoptionally positioned between the spring plates 165, and as is discussedin more detail below, may be rotated so as to push the spring plates 165apart, thereby withdrawing the pinch head 161 into the pinch head guide163. The release blade 169 may be manually operated, e.g., to disablethe occluder 147 in case of power loss, bladder 166 failure or othercircumstance.

Additional configurations and descriptions of certain components thatmay be instructive in constructing certain embodiments of the occluderare provided in U.S. Pat. No. 6,302,653. The spring plates 165 may beconstructed from any material that is elastically resistant to bendingforces and which has sufficient longitudinal stiffness (resistance tobending) to provide sufficient restoring force, in response to a bendingdisplacement, to occlude a desired number of collapsible tubes. In theillustrated embodiment, each spring plate is essentially flat whenunstressed and in the shape of a sheet or plate. In alternativeembodiments utilizing one or more resilient occluding members (springmembers), any occluding member(s) that is elastically resistant tobending forces and which has sufficient longitudinal stiffness(resistance to bending) to provide sufficient restoring force, inresponse to a bending displacement to occlude a desired number ofcollapsible tubes may be utilized. Potentially suitable spring memberscan have a wide variety of shapes as apparent to those of ordinary skillin the art, including, but not limited to cylindrical, prism-shaped,trapezoidal, square, or rectangular bars or beams, I-beams, ellipticalbeams, bowl-shaped surfaces, and others. Those of ordinary skill in theart can readily select proper materials and dimensions for spring plates165 based on the present teachings and the requirements of a particularapplication.

FIG. 40 shows a top view of the occluder 147 with the bladder 166deflated and the spring plates 165 located near each other and in a flator nearly flat condition. In this position, the pinch head 161 is fullyextended from the pinch head guide and the front panel of the cycler 14(i.e., the panel inside of the door 141) and enabled to occlude thepatient and drain lines. FIG. 41, on the other hand, shows the bladder166 in an inflated state in which the spring plates 165 are pushedapart, thereby retracting the pinch head 161 into the pinch head guide163. (Note that the linear adjustor 167 is fixed in place relative tothe cycler housing 82 and thus fixed relative to the front panel of thehousing 82. As the spring plates 165 are moved apart, the pinch head 161moves rearwardly relative to the front panel since the pinch head 161 isarranged to move freely in and out of the pinch head guide 163.) Thiscondition prevents the pinch head 161 from occluding the patient anddrain lines and is the condition in which the occluder 147 remainsduring normal operation of the cycler 14. That is, as discussed above,various components of the cycler 14 may operate using airpressure/vacuum, e.g., the control surface 148 may operate under thedrive of suitable air pressure/vacuum to cause fluid pumping and valveoperation for the cassette 24. Thus, when the cycler 14 is operatingnormally, the cycler 14 may produce sufficient air pressure to not onlycontrol system operation, but also to inflate the bladder 166 to retractthe pinch head 161 and prevent occlusion of the patient and drain lines.However, in the case of system shut down, failure, fault or othercondition, air pressure to the bladder 166 may be terminated, causingthe bladder 166 to deflate and the spring plates 165 to straighten andextend the pinch head 161 to occlude the lines. One possible advantageof the arrangement shown is that the return force of the spring plates165 is balanced such that the pinch head 161 generally will not bind inthe pinch head guide 163 when moving relative to the pinch head guide163. In addition, the opposing forces of the spring plates 165 will tendto reduce the amount of asymmetrical frictional wear of the pivot shaftsand bushings of the assembly. Also, once the spring plates 165 are in anapproximately straight position, the spring plates 165 can exert a forcein a direction generally along the length of the pinch head 161 that isseveral times larger than the force exerted by the bladder 166 on thespring plates 165 to separate the spring plates 165 from each other andretract the pinch head 161. Further, with the spring plates 165 in aflat or nearly flat condition, the force needed to be exerted by fluidin the collapsed tubing to overcome the pinching force exerted by thepinch head 161 approaches a relatively high force required, when appliedto the spring plates at their ends and essentially parallel to the planeof the flattened spring plates, to buckle the spring plates by breakingthe column stability of the flattened spring plates. As a result, theoccluder 147 can be very effective in occluding the lines with a reducedchance of failure while also requiring a relatively small force beapplied by the bladder 166 to retract the pinch head 161. The dualspring plate arrangement of the illustrative embodiment may have theadditional advantage of significantly increasing the pinching forceprovided by the pinch head, for any given force needed to bend thespring plate, and/or for any given size and thickness of spring plate.

In some circumstances, the force of the occluder 147 on the lines may berelatively large and may cause the door 141 to be difficult to open.That is, the door 141 must oppose the force of the occluder 147 when thepinch head 161 is in contact with and occluding lines, and in some casesthis may cause the latch that maintains the door 141 in a closed stateto be difficult or impossible to operate by hand. Of course, if thecycler 14 is started and produces air pressure to operate, the occluderbladder 166 can be inflated and the occluder pinch head 161 retracted.However, in some cases, such as with a pump failure in the cycler 14,inflation of the bladder 166 may be impossible or difficult. To allowopening of the door, the occluder 147 may include a manual release. Inthis illustrative embodiment, the occluder 147 may include a releaseblade 169 as shown in FIGS. 38 and 39 which includes a pair of wingspivotally mounted for rotary movement between the spring plates 165.When at rest, the release blade wings may be aligned with the springs asshown in FIG. 39, allowing the occluder to operate normally. However, ifthe spring plates 165 are in a flat condition and the pinch head 161needs to be retracted manually, the release blade 169 may be rotated,e.g., by engaging a hex key or other tool with the release blade 169 andturning the release blade 169, so that the wings push the spring plates165 apart. The hex key or other tool may be inserted through an openingin the housing 82 of the cycler 14, e.g., an opening near the left sidehandle depression in the cycler housing 82, and operated to disengagethe occluder 147 and allow the door 141 to be opened.

Pump Volume Delivery Measurement

In another aspect of the invention, the cycler 14 may determine a volumeof fluid delivered in various lines of the system 10 without the use ofa flowmeter, weight scale or other direct measurement of fluid volume orweight. For example, in one embodiment, a volume of fluid moved by apump, such as a pump in the cassette 24, may be determined based onpressure measurements of a gas used to drive the pump. In oneembodiment, a volume determination can be made by isolating two chambersfrom each other, measuring the respective pressures in the isolatedchambers, allowing the pressures in the chambers to partially orsubstantially equalize (by fluidly connecting the two chambers) andmeasuring the pressures. Using the measured pressures, the known volumeof one of the chambers, and an assumption that the equalization occursin an adiabatic way, the volume of the other chamber (e.g., a pumpchamber) can be calculated. In one embodiment, the pressures measuredafter the chambers are fluidly connected may be substantially unequal toeach other, i.e., the pressures in the chambers may not have yetcompletely equalized. However, these substantially unequal pressures maybe used to determine a volume of the pump control chamber, as explainedbelow.

For example, FIG. 42 shows a schematic view of a pump chamber 181 of thecassette 24 and associated control components and inflow/outflow paths.In this illustrative example, a liquid supply, which may include theheater bag 22, heater bag line 26 and a flow path through the cassette24, is shown providing a liquid input at the upper opening 191 of thepump chamber. The liquid outlet is shown in this example as receivingliquid from the lower opening 187 of the pump chamber 181, and mayinclude a flow path of the cassette 24 and the patient line 34, forexample. The liquid supply may include a valve, e.g., including thevalve port 192, that can be opened and closed to permit/impede flow toor from the pump chamber 181. Similarly, the liquid outlet may include avalve, e.g., including the valve port 190, that can be opened and closedto permit/impede flow to or from the pump chamber 181. Of course, theliquid supply could include any suitable arrangement, such as one ormore solution containers, the patient line, one or more flow paths inthe cassette 24 or other liquid source, and the liquid outlet couldlikewise include any suitable arrangement, such as the drain line, theheater bag and heater bag line, one or more flow paths in the cassette24 or other liquid outlet. Generally speaking, the pump chamber 181(i.e., on the left side of the membrane 14 in FIG. 42) will be filledwith an incompressible liquid, such as water or dialysate, duringoperation. However, air or other gas may be present in the pump chamber181 in some circumstances, such as during initial operation, priming, orother situations as discussed below. Also, it should be understood thatalthough aspects of the invention relating to volume and/or pressuredetection for a pump are described with reference to the pumparrangement of the cassette 24, aspects of the invention may be usedwith any suitable pump or fluid movement system.

FIG. 42 also shows schematically to the right of the membrane 15 and thecontrol surface 148 (which are adjacent each other) a control chamber171, which may be formed as a void or other space in the mating block170 associated with the pump control region 1482 of the control surface148 for the pump chamber 181, as discussed above. It is in the controlchamber 171 that suitable air pressure is introduced to cause themembrane 15/control region 1482 to move and effect pumping of liquid inthe pump chamber 181. The control chamber 171 may communicate with aline L0 that branches to another line L1 and a first valve X1 thatcommunicates with a pressure source (e.g., a source of air pressure orvacuum). The pressure source may include a piston pump in which thepiston is moved in a chamber to control a pressure delivered to thecontrol chamber 171, or may include a different type of pressure pumpand/or tank(s) to deliver suitable gas pressure to move the membrane15/control region 1482 and perform pumping action. The line L0 alsoleads to a second valve X2 that communicates with another line L2 and areference chamber (e.g., a space suitably configured for performing themeasurements described below). The reference chamber also communicateswith a line L3 having a valve X3 that leads to a vent or other referencepressure (e.g., a source of atmospheric pressure or other referencepressure). Each of the valves X1, X2 and X3 may be independentlycontrolled. Pressure sensors may be arranged, e.g., one sensor at thecontrol chamber 171 and another sensor at the reference chamber, tomeasure pressure associated with the control chamber and the referencechamber. These pressure sensors may be positioned and may operate todetect pressure in any suitable way. The pressure sensors maycommunicate with the control system 16 for the cycler 14 or othersuitable processor for determining a volume delivered by the pump orother features.

As mentioned above, the valves and other components of the pump systemshown in FIG. 42 can be controlled so as to measure pressures in thepump chamber 181, the liquid supply and/or liquid outlet, and/or tomeasure a volume of fluid delivered from the pump chamber 181 to theliquid supply or liquid outlet. Regarding volume measurement, onetechnique used to determine a volume of fluid delivered from the pumpchamber 181 is to compare the relative pressures at the control chamber171 to that of the reference chamber in two different pump states. Bycomparing the relative pressures, a change in volume at the controlchamber 171 can be determined, which corresponds to a change in volumein the pump chamber 181 and reflects a volume delivered from/receivedinto the pump chamber 181. For example, after the pressure is reduced inthe control chamber 171 during a pump chamber fill cycle (e.g., byapplying negative pressure from the pressure source through open valveX1) so as to draw the membrane 15 and pump control region 1482 intocontact with at least a portion of the control chamber wall (or toanother suitable position for the membrane 15/region 1482), valve X1 maybe closed to isolate the control chamber from the pressure source, andvalve X2 may be closed, thereby isolating the reference chamber from thecontrol chamber 171. Valve X3 may be opened to vent the referencechamber to ambient pressure, then closed to isolate the referencechamber. With valve X1 closed and the pressures in the control chamberand reference chamber measured, valve X2 is then opened to allow thepressure in the control chamber and the reference chamber to start toequalize. The initial pressures of the reference chamber and the controlchamber, together with the known volume of the reference chamber andpressures measured after equalization has been initiated (but not yetnecessarily completed) can be used to determine a volume for the controlchamber. This process may be repeated at the end of the pump deliverycycle when the sheet 15/control region 1482 are pushed into contact withthe spacer elements 50 of the pump chamber 181. By comparing the controlchamber volume at the end of the fill cycle to the volume at the end ofthe delivery cycle, a volume of liquid delivered from the pump can bedetermined.

Conceptually, the pressure equalization process (e.g., at opening of thevalve X2) is viewed as happening in an adiabatic way, i.e., without heattransfer occurring between air in the control and reference chambers andits environment. The conceptual notion is that there is an imaginarypiston located initially at the valve X2 when the valve X2 is closed,and that the imaginary piston moves in the line L0 or L2 when the valveX2 is opened to equalize the pressure in the control and referencechambers. Since (a) the pressure equalization process happens relativelyquickly, (b) the air in the control chamber and the reference chamberhas approximately the same concentrations of elements, and (c) thetemperatures are similar, the assumption that the pressure equalizationhappens in an adiabatic way may introduce only small error into thevolume measurements. Also, in one embodiment, the pressures taken afterequalization has been initiated may be measured before substantialequalization has occurred—further reducing the time between measuringthe initial pressures and the final pressures used to determine the pumpchamber volume. Error can be further reduced, for example, by using lowthermal conductivity materials for the membrane 15/control surface 148,the cassette 24, the control chamber 171, the lines, the referencechamber, etc., so as to reduce heat transfer.

Given the assumption that an adiabatic system exists between the statewhen the valve X2 is closed until after the valve X2 is opened and thepressures equalize, the following applies:PV^(γ)=Constant  (1)

where P is pressure, V is volume and γ is equal to a constant (e.g.,about 1.4 where the gas is diatomic, such as air). Thus, the followingequation can be written to relate the pressures and volumes in thecontrol chamber and the reference chamber before and after the openingof valve X2 and pressure equalization occurs:PrVr ^(γ) +PdVd ^(γ)=Constant=PfVf ^(γ)  (2)where Pr is the pressure in the reference chamber and lines L2 and L3prior to the valve X2 opening, Vr is the volume of the reference chamberand lines L2 and L3 prior to the valve X2 opening, Pd is the pressure inthe control chamber and the lines L0 and L1 prior to the valve X2opening, Vd is the volume of the control chamber and the lines L0 and L1prior to the valve X2 opening, Pf is the equalized pressure in thereference chamber and the control chamber after opening of the valve X2,and Vf is the volume of the entire system including the control chamber,the reference chamber and the lines L0, L1, L2, and L3, i.e., Vf=Vd+Vr.Since Pr, Vr, Pd, Pf and γ are known, and Vf=Vr+Vd, this equation can beused to solve for Vd. (Although reference is made herein, including inthe claims, to use of a “measured pressure” in determining volumevalues, etc., it should be understood that such a measured pressurevalue need not necessarily be any particular form, such as in psi units.Instead, a “measured pressure” or “determined pressure” may include anyvalue that is representative of a pressure, such as a voltage level, aresistance value, a multibit digital number, etc. For example, apressure transducer used to measure pressure in the pump control chambermay output an analog voltage level, resistance or other indication thatis representative of the pressure in the pump control chamber. The rawoutput from the transducer may be used as a measured pressure, and/orsome modified form of the output, such as a digital number generatedusing an analog output from the transducer, a psi or other value that isgenerated based on the transducer output, and so on. The same is true ofother values, such as a determined volume, which need not necessarily bein a particular form such as cubic centimeters. Instead, a determinedvolume may include any value that is representative of the volume, e.g.,could be used to generate an actual volume in, say, cubic centimeters.)

In an embodiment of a fluid management system (“FMS”) technique todetermine a volume delivered by the pump, it is assumed that pressureequalization upon opening of the valve X2 occurs in an adiabatic system.Thus, Equation 3 below gives the relationship of the volume of thereference chamber system before and after pressure equalization:Vrf=Vri(Pf/Patm)^(−(1/γ))  (3)

where Vrf is the final (post-equalization) volume of the referencechamber system including the volume of the reference chamber, the volumeof the lines L2 and L3 and the volume adjustment resulting from movementof the “piston”, which may move to the left or right of the valve X2after opening, Vri is the initial (pre-equalization) volume of thereference chamber and the lines L2 and L3 with the “piston” located atthe valve X2, Pf is the final equalized pressure after the valve X2 isopened, and Patm is the initial pressure of the reference chamber beforevalve X2 opening (in this example, atmospheric pressure). Similarly,Equation 4 gives the relationship of the volume of the control chambersystem before and after pressure equalization:Vdf=Vdi(Pf/Pdi)^(−(1/γ))  (4)

where Vdf is the final volume of the control chamber system includingthe volume of the control chamber, the volume of the lines L0 and L1,and the volume adjustment resulting from movement of the “piston”, whichmay move to the left or right of the valve X2 after opening, Vdi is theinitial volume of the control chamber and the lines L0 and L1 with the“piston” located at the valve X2, Pf is the final pressure after thevalve X2 is opened, and Pdi is the initial pressure of the controlchamber before valve X2 opening.

The volumes of the reference chamber system and the control chambersystem will change by the same absolute amount after the valve X2 isopened and the pressure equalizes, but will differ in sign (e.g.,because the change in volume is caused by movement of the “piston” leftor right when the valve X2 opens), as shown in Equation 5:ΔVr=(−1)ΔVd  (5)

(Note that this change in volume for the reference chamber and thecontrol chamber is due only to movement of the imaginary piston. Thereference chamber and control chamber will not actually change in volumeduring the equalization process under normal conditions.) Also, usingthe relationship from Equation 3, the change in volume of the referencechamber system is given by:ΔVr=Vrf−Vri=Vri(−1+(Pf/Patm)^(−(1/γ)))  (6)

Similarly, using Equation 4, the change in volume of the control chambersystem is given by:ΔVd=Vdf−Vdi=Vdi(−1+(Pf/Pdi)^(−(1/γ)))  (7)

Because Vri is known, and Pf and Patm are measured or known, ΔVr can becalculated, which according to Equation 5 is assumed to be equal to(−)ΔVd. Therefore, Vdi (the volume of the control chamber system beforepressure equalization with the reference chamber) can be calculatedusing Equation 7. In this embodiment, Vdi represents the volume of thecontrol chamber plus lines L0 and L1, of which L0 and L1 are fixed andknown quantities. Subtracting L0 and L1 from Vdi yields the volume ofthe control chamber alone. By using Equation 7 above, for example, bothbefore (Vdi1) and after (Vdi2) a pump operation (e.g., at the end of afill cycle and at the end of a discharge cycle), the change in volume ofthe control chamber can be determined, thus providing a measurement ofthe volume of fluid delivered by (or taken in by) the pump. For example,if Vdi1 is the volume of the control chamber at the end of a fillstroke, and Vdi2 is the volume of the control chamber at the end of thesubsequent delivery stroke, the volume of fluid delivered by the pumpmay be estimated by subtracting Vdi1 from Vdi2. Since this measurementis made based on pressure, the volume determination can be made fornearly any position of the membrane 15/pump control region 1482 in thepump chamber 181, whether for a full or partial pump stroke. However,measurement made at the ends of fill and delivery strokes can beaccomplished with little or no impact on pump operation and/or flowrate.

One aspect of the invention involves a technique for identifyingpressure measurement values that are to be used in determining a volumefor the control chamber and/or other purposes. For example, althoughpressure sensors may be used to detect a pressure in the control chamberand a pressure in the reference chamber, the sensed pressure values mayvary with opening/closing of valves, introduction of pressure to thecontrol chamber, venting of the reference chamber to atmosphericpressure or other reference pressure, etc. Also, since in oneembodiment, an adiabatic system is assumed to exist from a time beforepressure equalization between the control chamber and the referencechamber until after equalization, identifying appropriate pressurevalues that were measured as close together in time may help to reduceerror (e.g., because a shorter time elapsed between pressuremeasurements may reduce the amount of heat that is exchanged in thesystem). Thus, the measured pressure values may need to be chosencarefully to help ensure appropriate pressures are used for determininga volume delivered by the pump, etc.

For purposes of explanation, FIG. 43 shows a plot of illustrativepressure values for the control chamber and the reference chamber from apoint in time before opening of the valve X2 until some time after thevalve X2 is opened to allow the pressure in the chambers to equalize. Inthis illustrative embodiment, the pressure in the control chamber ishigher than the pressure in the reference chamber before equalization,but it should be understood that the control chamber pressure may belower than the reference chamber pressure before equalization in somearrangements, such as during and/or at the end of a fill stroke. Also,the plot in FIG. 43 shows a horizontal line marking the equalizationpressure, but it should be understood that this line is shown forclarity only. The equalization pressure in general will not be knownprior to opening of the valve X2. In this embodiment, the pressuresensors sense pressure at a rate of about 2000 Hz for both the controlchamber and the reference chamber, although other suitable samplingrates could be used. Before opening of the valve X2, the pressures inthe control chamber and the reference chamber are approximatelyconstant, there being no air or other fluid being introduced into thechambers. Thus, the valves X1 and X3 will generally be closed at a timebefore opening of the valve X2. Also, valves leading into the pumpchamber, such as the valve ports 190 and 192, may be closed to preventinfluence of pressure variations in the pump chamber, the liquid supplyor liquid outlet.

At first, the measured pressure data is processed to identify theinitial pressures for the control chamber and reference chambers, i.e.,Pd and Pr. In one illustrative embodiment, the initial pressures areidentified based on analysis of a 10-point sliding window used on themeasured pressure data. This analysis involves generating a best fitline for the data in each window (or set), e.g., using a least squarestechnique, and determining a slope for the best fit line. For example,each time a new pressure is measured for the control chamber or thereference chamber, a least squares fit line may be determined for a dataset including the latest measurement and the 9 prior pressuremeasurements. This process may be repeated for several sets of pressuredata, and a determination may be made as to when the slope of the leastsquares fit lines first becomes negative (or otherwise non-zero) andcontinues to grow more negative for subsequent data sets (or otherwisedeviates from a zero slope). The point at which the least squares fitlines begin to have a suitable, and increasing, non-zero slope may beused to identify the initial pressure of the chambers, i.e., at a timebefore the valve X2 is opened.

In one embodiment, the initial pressure value for the reference chamberand the control chamber may be determined to be in the last of 5consecutive data sets, where the slope of the best fit line for the datasets increases from the first data set to the fifth data set, and theslope of the best fit line for the first data set first becomes non-zero(i.e., the slope of best fit lines for data sets preceding the firstdata set is zero or otherwise not sufficiently non-zero). For example,the pressure sensor may take samples every ½ millisecond (or othersampling rate) starting at a time before the valve X2 opens. Every timea pressure measurement is made, the cycler 14 may take the most recentmeasurement together with the prior 9 measurements, and generate a bestfit line to the 10 data points in the set. Upon taking the next pressuremeasurement (e.g., ½ millisecond later), the cycler 14 may take themeasurement together with the 9 prior measurements, and again generate abest fit line to the 10 points in the set. This process may be repeated,and the cycler 14 may determine when the slope of the best fit line fora set of 10 data points first turns non-zero (or otherwise suitablysloped) and, for example, that the slope of the best fit line for 5subsequent sets of 10 data points increases with each later data set. Toidentify the specific pressure measurement to use, one technique is toselect the third measurement in the 5^(th) data set (i.e., the 5^(th)data set with which it was found that the best fit line has beenconsistently increasing in slope and the 1^(st) measurement is thepressure measurement that was taken earliest in time) as the measurementto be used as the initial pressure for the control chamber or thereference chamber, i.e., Pd or Pr. This selection was chosen usingempirical methods, e.g., plotting the pressure measurement values andthen selecting which point best represents the time when the pressurebegan the equalization process. Of course, other techniques could beused to select the appropriate initial pressure.

In one illustrative embodiment, a check may be made that the times atwhich the selected Pd and Pr measurements occurred were within a desiredtime threshold, e.g., within 1-2 milliseconds of each other. Forexample, if the technique described above is used to analyze the controlchamber pressure and the reference chamber pressure and identify apressure measurement (and thus a point in time) just before pressureequalization began, the times at which the pressures were measuredshould be relatively close to each other. Otherwise, there may have beenan error or other fault condition that invalidates one or both of thepressure measurements. By confirming that the time at which Pd and Proccurred are suitably close together, the cycler 14 may confirm that theinitial pressures were properly identified.

To identify when the pressures in the control chamber and the referencechamber have equalized such that measured pressures for the chamber canbe used to reliably determine pump chamber volume, the cycler 14 mayanalyze data sets including a series of data points from pressuremeasurements for both the control chamber and the reference chamber,determine a best fit line for each of the data sets (e.g., using a leastsquares method), and identify when the slopes of the best fit lines fora data set for the control chamber and a data set for the referencechamber are first suitably similar to each other, e.g., the slopes areboth close to zero or have values that are within a threshold of eachother. When the slopes of the best fit lines are similar or close tozero, the pressure may be determined to be equalized. The first pressuremeasurement value for either data set may be used as the final equalizedpressure, i.e., Pf. In one illustrative embodiment, it was found thatpressure equalization occurred generally within about 200-400milliseconds after valve X2 is opened, with the bulk of equalizationoccurring within about 50 milliseconds. Accordingly, the pressure in thecontrol and reference chambers may be sampled approximately 400-800times or more during the entire equalization process from a time beforethe valve X2 is opened until a time when equalization has been achieved.

In some cases, it may be desirable to increase the accuracy of thecontrol chamber volume measurement using an alternate FMS technique.Substantial differences in temperature between the liquid being pumped,the control chamber gas, and the reference chamber gas may introducesignificant errors in calculations based on the assumption that pressureequalization occurs adiabatically. Waiting to make pressure measurementsuntil full equalization of pressure between the control chamber and thereference chamber may allow an excessive amount of heat transfer tooccur. In one aspect of the invention, pressure values for the pumpchamber and reference chamber that are substantially unequal to eachother, i.e., that are measured before complete equalization hasoccurred, may be used to determine pump chamber volume.

In one embodiment, heat transfer may be minimized, and adiabaticcalculation error reduced, by measuring the chamber pressures throughoutthe equalization period from the opening of valve X2 through fullpressure equalization, and selecting a sampling point during theequalization period for the adiabatic calculations. In one embodiment ofan APD system, measured chamber pressures that are taken prior tocomplete pressure equalization between the control chamber and thereference chamber can be used to determine pump chamber volume. In oneembodiment, these pressure values may be measured about 50 ms after thechambers are first fluidly connected and equalization is initiated. Asmentioned above, in one embodiment, complete equalization may occurabout 200-400 ms after the valve X2 is opened. Thus, the measuredpressures may be taken at a point in time after the valve X2 is opened(or equalization is initiated) that is about 10% to 50% or less of thetotal equalization time period. Said another way, the measured pressuresmay be taken at a point in time at which 50-70% of pressure equalizationhas occurred (i.e., the reference and pump chamber pressures havechanged by about 50-70% of the difference between the initial chamberpressure and the final equalized pressure. Using a computer-enabledcontroller, a substantial number of pressure measurements in the controland reference chambers can be made, stored and analyzed during theequalization period (for example, 40-100 individual pressuremeasurements). Among the time points sampled during the first 50 ms ofthe equalization period, there is a theoretically optimized samplingpoint for conducting the adiabatic calculations (e.g., see FIG. 43 inwhich the optimized sampling point occurs at about 50 ms after openingof the valve X2). The optimized sampling point may occur at a time earlyenough after valve X2 opening to minimize thermal transfer between thegas volumes of the two chambers, but not so early as to introducesignificant errors in pressure measurements due to the properties of thepressure sensors and delays in valve actuation. However, as can be seenin FIG. 43, the pressures for the pump chamber and reference chambersmay be substantially unequal to each other at this point, and thusequalization may not be complete. (Note that in some cases, it may betechnically difficult to take reliable pressure measurements immediatelyafter the opening of valve X2, for example, because of the inherentinaccuracies of the pressure sensors, the time required for valve X2 tofully open, and the rapid initial change in the pressure of either thecontrol chamber or the reference chamber immediately after the openingof valve X2.)

During pressure equalization, when the final pressure for the controlchamber and reference chambers are not the same, Equation 2 becomes:PriVri ^(γ) +PdiVdi ^(γ)=Constant=PrfVrf ^(γ) +PdfVdf ^(γ)  (8)where: Pri=pressure in the reference chamber prior to opening valve X2,Pdi=pressure in the control chamber prior to opening valve X2, Prf=finalreference chamber pressure, Pdf=final control chamber pressure.

An optimization algorithm can be used to select a point in time duringthe pressure equalization period at which the difference between theabsolute values of ΔVd and ΔVr is minimized (or below a desiredthreshold) over the equalization period. (In an adiabatic process, thisdifference should ideally be zero, as indicated by Equation 5. In FIG.43 the point in time at which the difference between the absolute valuesof ΔVd and ΔVr is minimized occurs at the 50 ms line, marked “time atwhich final pressures identified.”) First, pressure data can becollected from the control and reference chambers at multiple points j=1through n between the opening of valve X2 and final pressureequalization. Since Vri, the fixed volume of the reference chambersystem before pressure equalization, is known, a subsequent value forVrj (reference chamber system volume at sampling point j after valve X2has opened) can be calculated using Equation 3 at each sampling pointPrj along the equalization curve. For each such value of Vrj, a valuefor ΔVd can be calculated using Equations 5 and 7, each value of Vrjthus yielding Vdij, a putative value for Vdi, the volume of the controlchamber system prior to pressure equalization. Using each value of Vrjand its corresponding value of Vdij, and using Equations 3 and 4, thedifference in the absolute values of ΔVd and ΔVr can be calculated ateach pressure measurement point along the equalization curve. The sum ofthese differences squared provides a measure of the error in thecalculated value of Vdi during pressure equalization for each value ofVrj and its corresponding Vdij. Denoting the reference chamber pressurethat yields the least sum of the squared differences of |ΔVd| and |ΔVr|as Prf, and its associated reference chamber volume as Vrf, the datapoints Prf and Pdf corresponding to Vrf can then be used to calculate anoptimized estimate of Vdi, the initial volume of the control chambersystem.

One method for determining where on the equalization curve to capture anoptimized value for Pdf and Prf is as follows:

-   -   1) Acquire a series of pressure data sets from the control and        reference chambers starting just before the opening of valve X2        and ending with Pr and Pd becoming close to equal. If Pri is the        first reference chamber pressure captured, then the subsequent        sampling points in FIG. 32 will be referred to as Prj=Pr1, Pr2,        . . . Prn.    -   2) Using Equation 6, for each Prj after Pri, calculate the        corresponding ΔVrj where j represents the jth pressure data        point after Pri.        ΔVrj=Vrj−Vri=Vri(−1+(Prj/Pri)^(−(1/γ))    -   3) For each such ΔVrj calculate the corresponding Vdij using        Equation 7. For example:

Δ Vr 1 = Vri * (−1 + (Pr  1/Pri)^(−(1/γ))) Δ Vd 1 = −Δ Vr 1Therefore, Vdi 1 = Δ Vd 1/(−1 + (Pd 1/Pdi)^(−(1/γ))) ⋮Vdin = Δ Vdn/(−1 + (Pdn/Pdi)^(−(1/γ)))Having calculated a set of n control chamber system initial volumes(Vdi1 to Vdin) based on the set of reference chamber pressure datapoints Pr1 to Prn during pressure equalization, it is now possible toselect the point in time (f) that yields an optimized measure of thecontrol chamber system initial volume (Vdi) over the entire pressureequalization period.

-   -   4) Using Equation 7, for each Vdi1 through Vdin, calculate all        ΔVdj,k using control chamber pressure measurements Pd for time        points k=1 to n.        -   For the Vdi corresponding to Pr1:

Δ Vd 1, 1 = Vdi 1 * (−1 + (Pd 1/Pd i)^(−(1/γ)))Δ Vd 1, 2 = Vdi 1 * (−1 + (Pd 2/Pdi)^(−(1/γ))) ⋮Δ Vd 1, n = Vdi 1 * (−1 + (Pdn/Pdi)^(−(1/γ))) ⋮For  the  Vdi  corresponding  to  Prn:Δ Vdn, 1 = Vdin * (−1 + (Pd 1/Pdi)^(−(1/γ)))Δ Vdn, 2 = Vdin * (−1 + (Pd 2/Pdi)^(−(1/γ))) ⋮Δ Vdn, n = Vdin * (−1 + (Pdn/Pdi)^(−(1/γ)))

-   -   5) Take the sum-square error between the absolute values of the        ΔVr's and ΔVdj,k's

$S_{1} = {\sum\limits_{k = 1}^{n}\left( {{{\Delta\; V_{{d\; 1},k}}} - {{\Delta\; V_{rk}}}} \right)^{2}}$

-   -   -   [S1 represents the sum-square error of |ΔVd| minus |ΔVr|            over all data points during the equalization period when            using the first data point Pr1 to determine Vdi, the control            chamber system initial volume, from Vr1 and ΔVr.]

$S_{2} = {\sum\limits_{k = 1}^{n}\left( {{{\Delta\; V_{{d\; 2},k}}} - {{\Delta\; V_{rk}}}} \right)^{2}}$

-   -   -   [S2 represents the sum-square error of |ΔVr| minus |ΔVd|            over all data points during the equalization period when            using the second data point Pr2 to determine Vdi, the            control chamber system initial volume, from Vr2 and ΔVr.]

⋮$S_{n} = {\sum\limits_{k = 1}^{n}\left( {{{\Delta\; V_{{dn},k}}} - {{\Delta\; V_{rk}}}} \right)^{2}}$

-   -   6) The Pr data point between Pr1 and Prn that generates the        minimum sum-square error S from step 5 (or a value that is below        a desired threshold) then becomes the chosen Prf, from which Pdf        and an optimized estimate of Vdi, the control chamber initial        volume, can then be determined. In this example, Pdf occurs at,        or about, the same time as Prf.    -   7) The above procedure can be applied any time that an estimate        of the control chamber volume is desired, but can preferably be        applied at the end of each fill stroke and each delivery stroke.        The difference between the optimized Vdi at the end of a fill        stroke and the optimized Vdi at the end of a corresponding        delivery stroke can be used to estimate the volume of liquid        delivered by the pump.

Air Detection

Another aspect of the invention involves the determination of a presenceof air in the pump chamber 181, and if present, a volume of air present.Such a determination can be important, e.g., to help ensure that apriming sequence is adequately performed to remove air from the cassette24 and/or to help ensure that air is not delivered to the patient. Incertain embodiments, for example, when delivering fluid to the patientthrough the lower opening 187 at the bottom of the pump chamber 181, airor other gas that is trapped in the pump chamber may tend to remain inthe pump chamber 181 and will be inhibited from being pumped to thepatient unless the volume of the gas is larger than the volume of theeffective dead space of pump chamber 181. As discussed below, the volumeof the air or other gas contained in pump chambers 181 can be determinedin accordance with aspects of the present invention and the gas can bepurged from pump chamber 181 before the volume of the gas is larger thanthe volume of the effective dead space of pump chamber 181.

A determination of an amount of air in the pump chamber 181 may be madeat the end of a fill stroke, and thus, may be performed withoutinterrupting a pumping process. For example, at the end of a fill strokeduring which the membrane 15 and the pump control region 1482 are drawnaway from the cassette 24 such that the membrane 15/region 1482 arebrought into contact with the wall of the control chamber 171, the valveX2 may be closed, and the reference chamber vented to atmosphericpressure, e.g., by opening the valve X3. Thereafter, the valves X1 andX3 may be closed, fixing the imaginary “piston” at the valve X2. Thevalve X2 may then be opened, allowing the pressure in the controlchamber and the reference chamber to equalize, as was described abovewhen performing pressure measurements to determine a volume for thecontrol chamber.

If there is no air bubble in the pump chamber 181, the change in volumeof the reference chamber, i.e., due to the movement of the imaginary“piston,” determined using the known initial volume of the referencechamber system and the initial pressure in the reference chamber, willbe equal to the change in volume of the control chamber determined usingthe known initial volume of the control chamber system and the initialpressure in the control chamber. (The initial volume of the controlchamber may be known in conditions where the membrane 15/control region1482 are in contact with the wall of the control chamber or in contactwith the spacer elements 50 of the pump chamber 181.) However, if air ispresent in the pump chamber 181, the change in volume of the controlchamber will actually be distributed between the control chamber volumeand the air bubble(s) in the pump chamber 181. As a result, thecalculated change in volume for the control chamber using the knowninitial volume of the control chamber system will not be equal to thecalculated change in volume for the reference chamber, thus signalingthe presence of air in the pump chamber.

If there is air in the pump chamber 181, the initial volume of thecontrol chamber system Vdi is actually equal to the sum of the volume ofthe control chamber and lines L0 and L1 (referred to as Vdfix) theinitial volume of the air bubble in the pump chamber 181, (referred toas Vbi), as shown in Equation 9:Vdi=Vbi+Vdfix  (9)

With the membrane 15/control region 1482 pressed against the wall of thecontrol chamber at the end of a fill stroke, the volume of any air spacein the control chamber, e.g., due to the presence of grooves or otherfeatures in the control chamber wall, and the volume of the lines L0 andL1—together Vdfix—can be known quite accurately. (Similarly, with themembrane 15/control region 1482 pressed against the spacer elements 50of the pump chamber 181, the volume of the control chamber and the linesL0 and L1 can be known accurately.) After a fill stroke, the volume ofthe control chamber system is tested using a positive control chamberpre-charge. Any discrepancy between this tested volume and the testedvolume at the end of the fill stroke may indicate a volume of airpresent in the pump chamber. Substituting from Equation 9 into Equation7, the change in volume of the control chamber ΔVd is given by:ΔVd=(Vbi+Vdfix)(−1+(Pdf/Pdi)^(−(1/γ)))  (10)

Since ΔVr can be calculated from Equation 6, and we know from Equation 5that ΔVr=(−1) ΔVd, Equation 10 can be re-written as:(−1)ΔVr=(Vbi+Vdfix)(−1+(Pdf/Pdi)^(−(1/γ)))  (11)and again as:Vbi=(−1)ΔVr/(−1+(Pdf/Pdi)^(−(1/γ)))−Vdfix  (12)

Accordingly, the cycler 14 can determine whether there is air in thepump chamber 181, and the approximate volume of the bubble usingEquation 12. This calculation of the air bubble volume may be performedif it is found, for example, that the absolute values of ΔVr (asdetermined from Equation 6) and ΔVd (as determined from Equation 7 usingVdi=Vdfix) are not equal to each other. That is, Vdi should be equal toVdfix if there is no air present in the pump chamber 181, and thus theabsolute value for ΔVd given by Equation 7 using Vdfix in place of Vdiwill be equal to ΔVr.

After a fill stroke has been completed, and if air is detected accordingto the methods described above, it may be difficult to determine whetherthe air is located on the pump chamber side or the control side of themembrane 15. Air bubbles could be present in the liquid being pumped, orthere could be residual air on the control (pneumatic) side of the pumpmembrane 15 because of a condition (such as, for example, an occlusion)during pumping that caused an incomplete pump stroke, and incompletefilling of the pump chamber. At this point, an adiabatic FMS measurementusing a negative pump chamber pre-charge can be done. If this FMS volumematches the FMS volume with the positive precharge, then the membrane isfree to move in both directions, which implies that the pump chamber isonly partially filled (possibly, for example, due to an occlusion). Ifthe value of the negative pump chamber pre-charge FMS volume equals thenominal control chamber air volume when the membrane 15/region 1482 isin contact with the inner wall of the control chamber, then it ispossible to conclude that there is an air bubble in the liquid on thepump chamber side of the flexible membrane.

Head Height Detection

In some circumstances, it may be useful to determine the heightwiselocation of the patient relative to the cassette 24 or other portion ofthe system. For example, dialysis patients in some circumstances cansense a “tugging” or other motion due to fluid flowing into or out ofthe patient's peritoneal cavity during a fill or drain operation. Toreduce this sensation, the cycler 14 may reduce the pressure applied tothe patient line 34 during fill and/or drain operations. However, tosuitably set the pressure for the patient line 34, the cycler 14 maydetermine the height of the patient relative to the cycler 14, theheater bag 22, drain or other portion of the system. For example, whenperforming a fill operation, if the patient's peritoneal cavity islocated 5 feet above the heater bag 22 or the cassette 24, the cycler 14may need to use a higher pressure in the patient line 34 to deliverdialysate than if the patient's peritoneal cavity is located 5 ft belowthe cycler 14. The pressure may be adjusted, for example, by alternatelyopening and closing a binary pneumatic source valve for variable timeintervals to achieve the desired target pump chamber pressure. Anaverage desired target pressure can be maintained, for example, byadjusting the time intervals to keep the valve open when the pumpchamber pressure is below the target pressure by a specified amount, andto keep the valve closed when the pump chamber pressure is above thetarget pressure by a specified amount. Any adjustments to maintain thedelivery of a complete stroke volume can be made by adjusting the filland/or delivery times of the pump chamber. If a variable orifice sourcevalve is used, the target pump chamber pressure can be reached byvarying the orifice of the source valve in addition to timing theintervals during which the valve is opened and closed. To adjust forpatient position, the cycler 14 may momentarily stop pumping of fluid,leaving the patient line 34 in open fluid communication with one or morepump chambers 181 in the cassette (e.g., by opening suitable valve portsin the cassette 24). However, other fluid lines may be closed, such asthe upper valve ports 192 for the pump chambers 181. In this condition,the pressure in the control chamber for one of the pumps may bemeasured. As is well known in the art, this pressure correlates with the“head” height of the patient, and can be used by the cycler 14 tocontrol the delivery pressure of fluid to the patient. A similarapproach can be used to determine the “head” height of the heater bag 22(which will generally be known), and/or the solution containers 20, asthe head height of these components may have an effect on pressureneeded for pumping fluid in a suitable way.

Noise Reduction Features of the Cycler

In accordance with aspects of the invention, the cycler 14 may includeone or more features to reduce noise generated by the cycler 14 duringoperation and/or when idle. In one aspect of the invention, the cycler14 may include a single pump that generates both pressure and vacuumthat are used to control the various pneumatic systems of the cycler 14.In one embodiment, the pump can simultaneously generate both pressureand vacuum, thereby reducing overall run time, and allowing the pump torun more slowly (and thus more quietly). In another embodiment, the airpump start and/or stop may be ramped, e.g., slowly increases pump speedor power output at starting and/or slowly decreases pump speed or poweroutput at shut down. This arrangement may help reduce “on/off” noiseassociated with start and stop of the air pump so pump noise is lessnoticeable. In another embodiment, the air pump may be operated at alower duty cycle when nearing a target output pressure or volume flowrate so that the air pump can continue operating as opposed to shuttingoff, only to be turned on after a short time. As a result, disruptioncaused by repeated on and off cycles of the air pump may be avoided.

FIG. 44 shows a perspective view of an interior section of the cycler 14with the upper portion of the housing 82 removed. In this illustrativeembodiment, the cycler 14 includes a single air pump 83, which includesthe actual pump and motor drive contained within a sound barrierenclosure. The sound barrier enclosure includes an outer shield, such asa metal or plastic frame, and a sound insulation material within theouter shield and at least partially surrounding the motor and pump. Thisair pump 83 may simultaneously provide air pressure and vacuum, e.g., toa pair of accumulator tanks 84. One of the tanks 84 may store positivepressure air, while the other stores vacuum. A suitable manifold andvalve arrangement may be coupled to the tanks 84 so as to provide andcontrol air pressure/vacuum supplied to the components of the cycler 14.

In accordance with another aspect of the invention, components thatrequire a relatively constant pressure or vacuum supply during cycleroperation, such as an occluder, may be isolated from the source of airpressure/vacuum at least for relatively long periods of time. Forexample, the occluder 147 in the cycler 14 generally requires a constantair pressure in the occluder bladder 166 so that the patient and drainlines remain open for flow. If the cycler 14 continues to operateproperly without power failure, etc., the bladder 166 may be inflatedonce at the beginning of system operation and remain inflated until shutdown. The inventors have recognized that in some circumstances airpowered devices that are relatively static, such as the bladder 166, may“creak” or otherwise make noise in response to slight variations insupplied air pressure. Such variations may cause the bladder 166 tochange size slightly, which causes associated mechanical parts to moveand potentially make noise. In accordance with an aspect of the bladder166 and other components having similar pneumatic power requirements,may be isolated from the air pump 83 and/or the tanks 84, e.g., by theclosing of a valve, so as to reduce variations of pressure in thebladder or other pneumatic component, thus reducing noise that may begenerated as a result of pressure variations. Another component that maybe isolated from the pneumatic supply is the bladder in the door 141 atthe cassette mounting location 145 which inflates to press the cassette24 against the control surface 148 when the door 141 is closed. Othersuitable components may be isolated as desired.

In accordance with another aspect of the invention, the speed and/orforce at which pneumatic components are actuated may be controlled to asto reduce noise generated by component operation. For example, movementof the valve control regions 1481 to move a corresponding portion of thecassette membrane 15 so as to open or close a valve port on the cassette24 may cause a “popping” noise as the membrane 15 slaps against and/orpull away from the cassette 24. Such noise may be reduced by controllingthe rate of operation of the valve control regions 1481, e.g., byrestricting the flow rate of air used to move the control regions 1481.Air flow may be restricted by, for example, providing a suitably smallsized orifice in the line leading to the associated control chamber, orin other ways.

A controller may also be programmed to apply pulse width modulation(“PWM”) to the activation of one or more pneumatic source valves at amanifold of cycler 14. The pneumatic pressure delivered to variousvalves and pumps of cassette 24 can be controlled by causing theassociated manifold source valves to open and close repeatedly duringthe period of actuation of a valve or pump in cassette 24. The rate ofrise or fall of pressure against membrane 15/control surface 148 canthen be controlled by modulating the duration of the “on” portion of theparticular manifold valve during the actuation period. An additionaladvantage of applying PWM to the manifold source valves is that variablepneumatic pressure can be delivered to the cassette 24 components usingonly a binary (on-off) source valve, rather than a more expensive andpotentially less reliable variable-orifice source valve.

In accordance with another aspect of the invention, the movement of oneor more valve elements may be suitably damped so as to reduce noisegenerated by valve cycling. For example, a fluid (such as a ferro fluid)may be provided with the valve element of high frequency solenoid valvesto damp the movement of the element and/or reduce noise generated bymovement of the valve element between open and closed positions.

In accordance with another embodiment, pneumatic control line vents maybe connected together and/or routed into a common, sound-insulated spaceso that noise associated with air pressure or vacuum release may bereduced. For example, when the occluder bladder 166 is vented to allowthe spring plates 165 to move toward each other and occlude one or morelines, the air pressure released may be released into a sound insulatedenclosure, as opposed to being released into a space where noiseassociated with the release may be heard more easily. In anotherembodiment, lines that are arranged to release air pressure may beconnected together with lines that are arranged to release an airvacuum. With this connection (which may include a vent to atmosphere, anaccumulator or other), noise generated by pressure/vacuum release may befurther reduced.

Control System

The control system 16 described in connection with FIG. 1 has a numberof functions, such as controlling dialysis therapy and communicatinginformation related to the dialysis therapy. While these functions maybe handled by a single computer or processor, it may be desirable to usedifferent computers for different functions so that the implementationsof those functions are kept physically and conceptually separate. Forexample, it may be desirable to use one computer to control the dialysismachinery and another computer to control the user interface.

FIG. 45 shows a block diagram illustrating an exemplary implementationof control system 16, wherein the control system comprises a computerthat controls the dialysis machinery (an “automation computer” 300) anda separate computer that controls the user interface (a “user interfacecomputer” 302). As will be described, safety-critical system functionsmay be run solely on the automation computer 300, such that the userinterface computer 302 is isolated from executing safety-criticalfunctions.

The automation computer 300 controls the hardware, such as the valves,heaters and pumps, that implement the dialysis therapy. In addition, theautomation computer 300 sequences the therapy and maintains a “model” ofthe user interface, as further described herein. As shown, theautomation computer 300 comprises a computer processing unit(CPU)/memory 304, a flash disk file system 306, a network interface 308,and a hardware interface 310. The hardware interface 310 is coupled tosensors/actuators 312. This coupling allows the automation computer 300to read the sensors and control the hardware actuators of the APD systemto monitor and perform therapy operations. The network interface 308provides an interface to couple the automation computer 300 to the userinterface computer 302.

The user interface computer 302 controls the components that enable dataexchange with the outside world, including the user and external devicesand entities. The user interface computer 302 comprises a computerprocessing unit (CPU)/memory 314, a flash disk file system 316, and anetwork interface 318, each of which may be the same as or similar totheir counterparts on the automation computer 300. The Linux operatingsystem may run on each of the automation computer 300 and the userinterface computer 302. An exemplary processor that may be suitable foruse as the CPU of the automation computer 300 and/or for use as the CPUof the user interface computer 302 is Freescale's Power PC 5200B®.

Via the network interface 318, the user interface computer 302 may beconnected to the automation computer 300. Both the automation computer300 and the user interface computer 302 may be included within the samechassis of the APD system. Alternatively, one or both computers or aportion of said computers (e.g., display 324) may be located outside ofthe chassis. The automation computer 300 and the user interface computer302 may be coupled by a wide area network, a local area network, a busstructure, a wireless connection, and/or some other data transfermedium.

The network interface 318 may also be used to couple the user interfacecomputer 302 to the Internet 320 and/or other networks. Such a networkconnection may be used, for example, to initiate connections to a clinicor clinician, upload therapy data to a remote database server, obtainnew prescriptions from a clinician, upgrade application software, obtainservice support, request supplies, and/or export data for maintenanceuse. According to one example, call center technicians may access alarmlogs and machine configuration information remotely over the Internet320 through the network interface 318. If desired, the user interfacecomputer 302 may be configured such that connections may only beinitiated by the user or otherwise locally by the system, and not byremote initiators.

The user interface computer 302 also comprises a graphics interface 322that is coupled to a user interface, such as the user interface 144described in connection with FIG. 10. According to one exemplaryimplementation, the user interface comprises a display 324 that includesa liquid crystal display (LCD) and is associated with a touchscreen. Forexample, a touchscreen may be overlaid on the LCD so that the user canprovide inputs to the user interface computer 302 by touching thedisplay with a finger, stylus or the like. The display may also beassociated with an audio system capable of playing, among other things,audio prompts and recorded speech. The user may adjust the brightness ofthe display 324 based on their environment and preference. Optionally,the APD system may include a light sensor, and the brightness of thedisplay may be adjusted automatically in response to the amount ofambient light detected by the light sensor.

In addition, the user interface computer 302 comprises a USB interface326. A data storage device 328, such as a USB flash drive, may beselectively coupled to the user interface computer 302 via the USBinterface 326. The data storage device 328 may comprise a “patient datakey” used to store patient-specific data. Data from dialysis therapiesand/or survey questions (e.g., weight, blood pressure) may be logged tothe patient data key. In this way, patient data may be accessible to theuser interface computer 302 when coupled to the USB interface 326 andportable when removed from the interface. The patient data key may beused for transferring data from one system or cycler to another during acycler swap, transferring new therapy and cycler configuration data fromclinical software to the system, and transferring treatment history anddevice history information from the system to clinical software. Anexemplary patient data key 325 is shown in FIG. 65.

As shown, the patient data key 325 comprises a connector 327 and ahousing 329 coupled to the connector. The patient data key 325 may beoptionally be associated with a dedicated USB port 331. The port 331comprises a recess 333 (e.g., in the chassis of the APD system) and aconnector 335 disposed within the recess. The recess may be defined, atleast in part, by a housing 337 associated with the port 331. Thepatient data key connector 327 and the port connector 335 are adapted tobe selectively electrically and mechanically coupled to each other. Asmay be appreciated from FIG. 65, when the patient data key connector 327and the port connector 335 are coupled, the housing 329 of the patientdata storage device 325 is received at least partially within the recess333.

The housing 329 of the patient data key 325 may include visual cuesindicative of the port with which it is associated and/or be shaped toprevent incorrect insertion. For example, the recess 333 and/or housing337 of the port 331 may have a shape corresponding to the shape of thehousing 329 of the patient data key 325. For example, each may have anon-rectangular or otherwise irregular shape, such as an oblong shapewith an upper indentation as shown in FIG. 65. The recess 333 and/orhousing 337 of the port 331 and the housing 329 of the patient data key325 may include additional visual cues to indicate their association.For example, each may be formed of the same material and/or have thesame or a similar color and/or pattern.

Alternatively or additionally, the patient data key 325 may comprise averification code that is readable by the APD system to verify that thepatient data key is of an expected type and/or origin. Such averification code may be stored in a memory of the patient data key 325,and be read from the patient data key and processed by a processor ofthe APD system. Alternatively or additionally, such a verification codemay be included on an exterior of the patient data key 325, e.g., as abarcode or numeric code. In this case, the code may be read by a cameraand associated processor, a barcode scanner, or another code readingdevice.

If the patient data key is not inserted when the system is powered on,an alert may be generated requesting that the key be inserted. However,the system may be able to run without the patient data key as long as ithas been previously configured. Thus, a patient who has lost theirpatient data key may receive therapy until a replacement key can beobtained. Data may be stored directly to the patient data key ortransferred to the patient data key after storage on the user interfacecomputer 302. Data may also be transferred from the patient data key tothe user interface computer 302.

In addition, a USB Bluetooth® adapter 330 may be coupled to the userinterface computer 302 via the USB interface 326 to allow, for example,data to be exchanged with nearby Bluetooth-enabled devices. For example,a Bluetooth® —enabled scale in the vicinity of the APD system maywirelessly transfer information concerning a patient's weight to thesystem via the USB interface 326 using the USB Bluetooth® adapter 330.Similarly, a Bluetooth® —enabled blood pressure cuff may wirelesslytransfer information concerning a patient's blood pressure to the systemusing the USB Bluetooth® adapter 330. The Bluetooth® adapter may bebuilt-in to the user interface computer 302 or may be external (e.g., aBluetooth® dongle).

The USB interface 326 may comprise several ports, and these ports mayhave different physical locations and be used for different USB device.For example, it may be desirable to make the USB port for the patientdata key accessible from the front of the machine, while another USBport may be provided at and accessible from the back of the machine. AUSB port for the Bluetooth® connection may be included on the outside ofthe chassis, or instead be located internal to the machine or inside thebattery door, for example.

As noted above, functions that could have safety-critical implicationsmay be isolated on the automation computer. Safety-critical informationrelates to operations of the APD system. For example, safety-criticalinformation may comprise a state of a APD procedure and/or thealgorithms for implementing or monitoring therapies. Non safety-criticalinformation may comprise information that relates to the visualpresentation of the screen display that is not material to theoperations of the APD system.

By isolating functions that could have safety-critical implications onthe automation computer 300, the user interface computer 302 may berelieved of handling safety-critical operations. Thus, problems with orchanges to the software that executes on the user interface computer 302will not affect the delivery of therapy to the patient. Consider theexample of graphical libraries (e.g., Trolltech's Qt® toolkit), whichmay be used by the user interface computer 302 to reduce the amount oftime needed to develop the user interface view. Because these librariesare handled by a process and processor separate from those of theautomation computer 300, the automation computer is protected from anypotential flaws in the libraries that might affect the rest of thesystem (including safety-critical functions) were they handled by thesame processor or process.

Of course, while the user interface computer 302 is responsible for thepresentation of the interface to the user, data may also be input by theuser using the user interface computer 302, e.g., via the display 324.To maintain the isolation between the functions of the automationcomputer 300 and the user interface computer 302, data received via thedisplay 324 may be sent to the automation computer for interpretationand returned to the user interface computer for display.

Although FIG. 45 shows two separate computers, separation of the storageand/or execution of safety-critical functions from the storage and/orexecution of non safety-critical functions may be provided by having asingle computer including separate processors, such as CPU/memorycomponents 304 and 314. Thus, it should be appreciated that providingseparate processors or “computers” is not necessary. Further, a singleprocessor may alternatively be used to perform the functions describedabove. In this case, it may be desirable to functionally isolate theexecution and/or storage of the software components that control thedialysis machinery from those that control the user interface, althoughthe invention is not limited in this respect.

Other aspects of the system architecture may also be designed to addresssafety concerns. For example, the automation computer 300 and userinterface computer 302 may include a “safe line” that can be enabled ordisabled by the CPU on each computer. The safe line may be coupled to avoltage supply that generates a voltage (e.g., 12 V) sufficient toenable at least some of the sensors/actuators 312 of the APD system.When both the CPU of the automation computer 300 and the CPU of the userinterface computer 302 send an enable signal to the safe line, thevoltage generated by the voltage supply may be transmitted to thesensors/actuators to activate and disable certain components. Thevoltage may, for example, activate the pneumatic valves and pump,disable the occluder, and activate the heater. When either CPU stopssending the enable signal to the safe line, the voltage pathway may beinterrupted (e.g., by a mechanical relay) to deactivate the pneumaticvalves and pump, enable the occluder, and deactivate the heater. In thisway, when either the automation computer 300 or the user interfacecomputer 302 deems it necessary, the patient may be rapidly isolatedfrom the fluid path, and other activities such as heating and pumpingmay be stopped. Each CPU can disable the safe line at any time, such aswhen a safety-critical error is detected or a software watchdog detectsan error. The system may be configured such that, once disabled, thesafe line may not be re-enabled until both the automation computer 300and user interface computer 302 have completed self-tests.

FIG. 46 shows a block diagram of the software subsystems of the userinterface computer 302 and the automation computer 300. In this example,a “subsystem” is a collection of software, and perhaps hardware,assigned to a specific set of related system functionality. A “process”may be an independent executable which runs in its own virtual addressspace, and which passes data to other processes using inter-processcommunication facilities.

The executive subsystem 332 includes the software and scripts used toinventory, verify, start and monitor the execution of the softwarerunning on the CPU of the automation computer 300 and the CPU of theuser interface computer 302. A custom executive process is run on eachof the foregoing CPUs. Each executive process loads and monitors thesoftware on its own processor and monitors the executive on the otherprocessor.

The user interface (UI) subsystem 334, handles system interactions withthe user and the clinic. The UI subsystem 334 is implemented accordingto a “model-view-controller” design pattern, separating the display ofthe data (“view”) from the data itself (“model”). In particular, systemstate and data modification functions (“model”) and cycler controlfunctions (“controller”) are handled by the UI model and cyclercontroller 336 on the automation computer 300, while the “view” portionof the subsystem is handled by the UI screen view 338 on the UI computer302. Data display and export functionality, such as log viewing orremote access, may be handled entirely by the UI screen view 338. The UIscreen view 338 monitors and controls additional applications, such asthose that provide log viewing and a clinician interface. Theseapplications are spawned in a window controlled by the UI screen view338 so that control can be returned to the UI screen view 338 in thecase of an alert, an alarm or an error.

The therapy subsystem 340 directs and times the delivery of the dialysistreatment. It may also be responsible verifying a prescription,calculating the number and duration of therapy cycles based upon theprescription, time and available fluids, controlling the therapy cycles,tracking fluid in the supply bags, tracking fluid in the heater bag,tracking the amount of fluid in the patient, tracking the amount ofultra-filtrate removed from patient, and detecting alert or alarmconditions.

The machine control subsystem 342 controls the machinery used toimplement the dialysis therapy, orchestrating the high level pumping andcontrol functionality when called upon by the therapy subsystem 340. Inparticular, the following control functions may be performed by themachine control subsystem 342: air compressor control; heater control;fluid delivery control (pumping); and fluid volume measurement. Themachine control subsystem 342 also signals the reading of sensors by theI/O subsystem 344, described below.

The I/O subsystem 344 on the automation computer 300 controls access tothe sensors and actuators used to control the therapy. In thisimplementation, the I/O subsystem 344 is the only application processwith direct access to the hardware. Thus, the I/O subsystem 344publishes an interface to allow other processes to obtain the state ofthe hardware inputs and set the state of the hardware outputs.

The database subsystem 346, also on the user interface computer 302,stores all data to and retrieves all data from the databases used forthe onboard storage of machine, patient, prescription, user-entry andtreatment history information. This provides a common access point whensuch information is needed by the system. The interface provided by thedatabase subsystem 346 is used by several processes for their datastorage needs. The database subsystem 346 also manages database filemaintenance and back-up.

The UI screen view 338 may invoke a therapy log query application tobrowse the therapy history database. Using this application, which mayalternatively be implemented as multiple applications, the user cangraphically review their treatment history, their prescription and/orhistorical machine status information. The application transmitsdatabase queries to the database subsystem 346. The application can berun while the patient is dialyzing without impeding the safe operationof the machine.

The remote access application, which may be implemented as a singleapplication or multiple applications, provides the functionality toexport therapy and machine diagnostic data for analysis and/or displayon remote systems. The therapy log query application may be used toretrieve information requested, and the data may be reformatted into amachine neutral format, such as XML, for transport. The formatted datamay be transported off-board by a memory storage device, direct networkconnection or other external interface 348. Network connections may beinitiated by the APD system, as requested by the user.

The service interface 356 may be selected by the user when a therapy isnot in progress. The service interface 356 may comprise one or morespecialized applications that log test results and optionally generate atest report which can be uploaded, for example, to a diagnostic center.The media player 358 may, for example, play audio and/or video to bepresented to a user.

According to one exemplary implementation, the databases described aboveare implemented using SQLite, a software library that implements aself-contained, server-less, zero-configuration, transactional SQLdatabase engine.

The executive subsystem 332 implements two executive modules, the userinterface computer (UIC) executive 352 on the user interface computer302 and the automation computer (AC) executive 354 on the automationcomputer 300. Each executive is started by the startup scripts that runafter the operating system is booted and includes a list of processes itstarts. As the executives go through their respective process lists,each process image is checked to ensure its integrity in the file systembefore the process is launched. The executives monitor each childprocess to ensure that each starts as expected and continue monitoringthe child processes while they run, e.g., using Linux parent-childprocess notifications. When a child process terminates or fails, theexecutive either restarts it (as in the case of the UI view) or placesthe system in fail safe mode to ensure that the machine behaves in asafe manner. The executive processes are also responsible for cleanlyshutting down the operating system when the machine is powering off.

The executive processes communicate with each other allowing them tocoordinate the startup and shutdown of the various applicationcomponents. Status information is shared periodically between the twoexecutives to support a watchdog function between the processors. Theexecutive subsystem 332 is responsible for enabling or disabling thesafe line. When both the UIC executive 352 and the AC executive 354 haveenabled the safe line, the pump, the heater, and the valves can operate.Before enabling the lines, the executives test each line independentlyto ensure proper operation. In addition, each executive monitors thestate of the other's safe line.

The UIC executive 352 and the AC executive 354 work together tosynchronize the time between the user interface computer 302 and theautomation computer 300. The time basis is configured via a batterybacked real-time clock on the user interface computer 302 that isaccessed upon startup. The user interface computer 302 initializes theCPU of the automation computer 300 to the real-time clock. After that,the operating system on each computer maintains its own internal time.The executives work together to ensure sufficiently timekeeping byperiodically performing power on self tests. An alert may be generatedif a discrepancy between the automation computer time and the userinterface computer time exceeds a given threshold.

FIG. 47 shows the flow of information between various subsystems andprocesses of the APD system. As discussed previously, the UI model 360and cycler controller 362 run on the automation computer. The userinterface design separates the screen display, which is controlled bythe UI view 338, from the screen-to-screen flow, which is controlled bythe cycler controller 362, and the displayable data items, which arecontrolled by the UI model 360. This allows the visual representation ofthe screen display to be changed without affecting the underlyingtherapy software. All therapy values and context are stored in the UImodel 360, isolating the UI view 338 from the safety-critical therapyfunctionality.

The UI model 360 aggregates the information describing the current stateof the system and patient, and maintains the information that can bedisplayed via the user interface. The UI model 360 may update a statethat is not currently visible or otherwise discernable to the operator.When the user navigates to a new screen, the UI model 360 provides theinformation relating to the new screen and its contents to the UI view338. The UI model 360 exposes an interface allowing the UI view 338 orsome other process to query for current user interface screen andcontents to display. The UI model 360 thus provides a common point whereinterfaces such as the remote user interface and online assistance canobtain the current operational state of the system.

The cycler controller 362 handles changes to the state of the systembased on operator input, time and therapy layer state. Acceptablechanges are reflected in the UI model 360. The cycler controller 362 isimplemented as a hierarchical state machine that coordinates therapylayer commands, therapy status, user requests and timed events, andprovides view screen control via UI model 360 updates. The cyclercontroller 362 also validates user inputs. If the user inputs areallowed, new values relating to the user inputs are reflected back tothe UI view 338 via the UI model 360. The therapy process 368 acts as aserver to the cycler controller 362. Therapy commands from the cyclercontroller 362 are received by the therapy process 368.

The UI view 338, which runs on the UI computer 302, controls the userinterface screen display and responds to user input from the touchscreen. The UI view 338 keeps track of local screen state, but does notmaintain machine state information. Machine state and displayed datavalues, unless they are in the midst of being changed by the user, aresourced from the UI model 360. If the UI view 338 terminates and isrestarted, it displays the base screen for the current state withcurrent data. The UI view 338 determines which class of screens todisplay from the UI model 360, which leaves the presentation of thescreen to the UI view. All safety-critical aspects of the user interfaceare handled by the UI model 360 and cycler controller 362.

The UI view 338 may load and execute other applications 364 on the userinterface computer 302. These applications may perform non-therapycontrolling tasks. Exemplary applications include the log viewer, theservice interface, and the remote access applications. The UI view 338places these applications within a window controlled by the UI view,which allows the UI view to display status, error, and alert screens asappropriate. Certain applications may be run during active therapy. Forexample, the log viewer may be run during active therapy, while theservice interface and the remote access application generally may not.When an application subservient to the UI view 338 is running and theuser's attention is required by the ongoing therapy, the UI view 338 maysuspend the application and regain control of the screen and inputfunctions. The suspended application can be resumed or aborted by the UIview 338.

FIG. 48 illustrates the operation of the therapy subsystem 340 describedin connection with FIG. 46. The therapy subsystem 340 functionality isdivided across three processes: therapy control; therapy calculation;and solution management. This allows for functional decomposition, easeof testing, and ease of updates.

The therapy control module 370 uses the services of the therapycalculation module 372, solution management module 374 and machinecontrol subsystem 342 (FIG. 46) to accomplish its tasks.Responsibilities of the therapy control module 370 include trackingfluid volume in the heater bag, tracking fluid volume in the patient,tracking patient drain volumes and ultra filtrate, tracking and loggingcycle volumes, tracking and logging therapy volumes, orchestrating theexecution of the dialysis therapy (drain-fill-dwell), and controllingtherapy setup operations. The therapy control module 370 performs eachphase of the therapy as directed by the therapy calculation module 370.

The therapy calculation module 370 tracks and recalculates thedrain-fill-dwell cycles that comprise a peritoneal dialysis therapy.Using the patient's prescription, the therapy calculation module 372calculates the number of cycles, the dwell time, and the amount ofsolution needed (total therapy volume). As the therapy proceeds, asubset of these values is recalculated, accounting for the actualelapsed time. The therapy calculation module 372 tracks the therapysequence, passing the therapy phases and parameters to the therapycontrol module 370 when requested.

The solution management module 374 maps the placement of solution supplybags, tracks the volume in each supply bag, commands the mixing ofsolutions based upon recipes in the solution database, commands thetransfer of the requested volume of mixed or unmixed solution into theheater bag, and tracks the volume of mixed solutions available using thesolution recipe and available bag volume.

FIG. 49 shows a sequence diagram depicting exemplary interactions of thetherapy module processes described above during the initial replenishand dialyze portions of the therapy. During the exemplary initialreplenish process 376, the therapy control module 370 fetches thesolution ID and volume for the first fill from the therapy calculationmodule 372. The solution ID is passed to the solution management module374 with a request to fill the heater bag with solution, in preparationfor priming the patient line and the first patient fill. The solutionmanagement module 374 passes the request to the machine controlsubsystem 342 to begin pumping the solution to the heater bag.

During the exemplary dialyze process 378, the therapy control module 370executes one cycle (initial drain, fill, dwell-replenish, and drain) ata time, sequencing these cycles under the control of the therapycalculation module 372. During the therapy, the therapy calculationmodule 372 is updated with the actual cycle timing, so that it canrecalculate the remainder of the therapy if needed.

In this example, the therapy calculation module 372 specifies the phaseas “initial drain,” and the therapy control module makes the request tothe machine control subsystem 342. The next phase specified by thetherapy calculation module 372 is “fill.” The instruction is sent to themachine control subsystem 342. The therapy calculation module 372 iscalled again by the therapy control module 370, which requests thatfluid be replenished to the heater bag during the “dwell” phase. Thesolution management module 374 is called by the therapy control module370 to replenish fluid in the heater bag by calling the machine controlsubsystem 342. Processing continues with therapy control module 370calling the therapy calculation module 372 to get the next phase. Thisis repeated until there are no more phases, and the therapy is complete.

Alert/Alarm Functions

Conditions or events in the APD system may trigger alerts and/or alarmsthat are logged, displayed to a user, or both. These alerts and alarmsare a user interface construct that reside in the user interfacesubsystem, and may be triggered by conditions that occur in any part ofthe system. These conditions may be grouped into three categories: (1)system error conditions, (2) therapy conditions, and (3) systemoperation conditions.

“System error conditions” relate to errors detected in software, memory,or other aspects of the processors of the APD system. These errors callthe reliability of the system into question, and may be considered“unrecoverable.” System error conditions cause an alarm that isdisplayed or otherwise made known to the user. The alarm may also belogged. Since system integrity cannot be guaranteed in the instance of asystem error condition, the system may enter a fail safe mode in whichthe safe line described herein is disabled.

Each subsystem described in connection with FIG. 46 is responsible fordetecting its own set of system errors. System errors between subsystemsare monitored by the user interface computer executive 352 andautomation computer executives 354. When a system error originates froma process running on the user interface computer 302, the processreporting the system error terminates. If the UI screen view subsystem338 is terminated, the user interface computer executive 352 attempts torestart it, e.g., up to a maximum of three times. If it fails to restartthe UI screen view 338 and a therapy is in progress, the user interfacecomputer executive 352 transitions the machine to a fail safe mode.

When a system error originates from a process running on the automationcomputer 300, the process terminates. The automation computer executive354 detects that the process has terminated and transitions to a safestate if a therapy is in progress.

When a system error is reported, an attempt is made to inform the user,e.g., with visual and/or audio feedback, as well as to log the error toa database. System error handling is encapsulated in the executivesubsystem 332 to assure uniform handling of unrecoverable events. Theexecutive processes of the UIC executive 352 and AC executive 354monitor each other such that if one executive process fails duringtherapy, the other executive transitions the machine to a safe state.

“Therapy conditions” are caused by a status or variable associated withthe therapy going outside of allowable bounds. For example, a therapycondition may be caused by an out-of-bounds sensor reading. Theseconditions may be associated with an alert or an alarm, and then logged.Alarms are critical events, generally requiring immediate action. Alarmsmay be prioritized, for example as low, medium or high, based on theseverity of the condition. Alerts are less critical than alarms, andgenerally do not have any associated risk other than loss of therapy ordiscomfort. Alerts may fall into one of three categories: messagealerts, escalating alerts, and user alerts.

The responsibility for detecting therapy conditions that may cause analarm or alert condition is shared between the UI model and therapysubsystems. The UI model subsystem 360 (FIG. 47) is responsible fordetecting alarm and alert conditions pre-therapy and post-therapy. Thetherapy subsystem 340 (FIG. 46) is responsible for detecting alarm andalert conditions during therapy.

The responsibility for handling alerts or alarms associated with therapyconditions is also shared between the UI model and therapy subsystems.Pre-therapy and post-therapy, the UI model subsystem 360 is responsiblefor handling the alarm or alert condition. During a therapy session, thetherapy subsystem 340 is responsible for handling the alarm or alertcondition and notifying the UI Model Subsystem an alarm or alertcondition exists. The UI model subsystem 360 is responsible forescalating alerts, and for coordinating with the UI view subsystem 338to provide the user with visual and/or audio feedback when an alarm oralert condition is detected.

“System operation conditions” do not have an alert or alarm associatedwith them. These conditions are simply logged to provide a record ofsystem operations. Auditory or visual feedback need not be provided.

Actions that may be taken in response to the system error conditions,therapy conditions, or system operation conditions described above areimplemented by the subsystem (or layer) that detected the condition,which sends the status up to the higher subsystems. The subsystem thatdetected the condition may log the condition and take care of any safetyconsiderations associated with the condition. These safetyconsiderations may comprise any one or combination of the following:pausing the therapy and engaging the occluder; clearing states andtimers as needed; disabling the heater; ending the therapy entirely;deactivating the safe line to close the occluder, shut off the heater,and removing power from the valves; and preventing the cycler fromrunning therapies even after a power cycle to require the system to besent back to service. The UI subsystem 334 may be responsible forconditions that can be cleared automatically (i.e., non-latchingconditions) and for user recoverable conditions that are latched and canonly be cleared by user interaction.

Each condition may be defined such that it contains certain informationto allow the software to act according to the severity of the condition.This information may comprise a numeric identifier, which may be used incombination with a lookup table to define priority; a descriptive nameof the error (i.e., a condition name); the subsystem that detected thecondition; a description of what status or error triggers the condition;and flags for whether the condition implements one or more actionsdefined above.

Conditions may be ranked in priority such that when multiple conditionsoccur, the higher priority condition may be handled first. This priorityranking may be based on whether the condition stops the administrationof therapy. When a condition occurs that stops therapy, this conditiontakes precedence when relaying status to the next higher subsystem. Asdiscussed above, the subsystem that detects a condition handles thecondition and sends status information up to the subsystem above. Basedon the received status information, the upper subsystem may trigger adifferent condition that may have different actions and a differentalert/alarm associated with it. Each subsystem implements any additionalactions associated with the new condition and passes status informationup to the subsystem above. According to one exemplary implementation,the UI subsystem only displays one alert/alarm at a given time. In thiscase, the UI model sorts all active events by their priority anddisplays the alert/alarm that is associated with the highest priorityevent.

A priority may be assigned to an alarm based on the severity thepotential harm and the onset of that harm. Table 1, below, shows anexample of how priorities may be assigned in this manner.

TABLE 1 POTENTIAL RESULT OF FAILURE TO RESPOND TO THE CAUSE OF ALARMONSET OF POTENTIAL HARM CONDITION IMMEDIATE PROMPT DELAYED death orirreversible high priority high priority medium priority injuryreversible injury high priority medium low priority priority minordiscomfort or medium priority low priority low priority or no injuryalarm signal

In the context of Table 1, the onset of potential harm refers to when aninjury occurs and not to when it is manifested. A potential harm havingan onset designated as “immediate” denotes a harm having the potentialto develop within a period of time not usually sufficient for manualcorrective action. A potential harm having an onset designated as“prompt” denotes a harm having the potential to develop within a periodof time usually sufficient for manual corrective action. A potentialharm having an onset designated as “delayed” denotes a harm having thepotential to develop within an unspecified time greater than that givenunder “prompt.”

FIGS. F-K show exemplary screen views relating to alerts and alarms thatmay be displayed on a touch screen user interface. FIG. 50 shows thefirst screen of an alarm, which includes a diagram 380 and text 382instructing a user to close their transfer set. The screen includes avisual warning 384, and is also associated with an audio warning. Theaudio warning may be turned off my selecting the “audio off” option 386on the touch screen. When the user has closed the transfer set, the userselects the “confirm” option 388 on the touch screen. FIG. 51 shows asimilar alarm screen instructing a user to close their transfer set. Inthis case, an indication that draining is paused 390 and an instructionto select “end treatment” are provided 392.

As previously discussed, alerts generally do not have associated riskother than loss of therapy or discomfort. Thus, an alert may or may notcause the therapy to pause. Alerts can be either “auto recoverable,”such that if the event clears the alert automatically clears, or “userrecoverable,” such that user interaction with the user interface isneeded to clear the alert. An audible alert prompt, which may have avolume that may be varied within certain limits, may be used to bring analert to the attention of a user. In addition, information or aninstruction may be displayed to the user. So that such information orinstruction may be viewed by the user, an auto-dim feature of the userinterface may be disabled during alerts.

In order to reduce the amount of disturbance the user, alerts can may becategorized into different types based on how important an alert is andhow quick a user response is required. Three exemplary types of alertsare a “message alert,” an “escalating alert,” and a “user alert.” Thesealerts have different characteristics based on how information isvisually presented to the user and how the audible prompt is used.

A “message alert” may appear at the top of a status screen and is usedfor informational purposes when a user interaction is not required.Because no action needs to be taken to clear the alert, an audibleprompt is generally not used to avoid disturbing, and possibly waking,the patient. However, an audible alert may be optionally presented. FIG.52 shows an exemplary message alert. In particular, FIG. 52 shows anunder-temperature message alert 394 that may be used to inform a userwhen the dialysate is below a desired temperature or range. In thiscase, a user does not need to take any action, but is informed thattherapy will be delayed while the dialysate is heated. If the patientdesires more information, the “view” option 396 may be selected on thetouch screen. This causes additional information 398 concerning thealert to appear on the screen, as shown in FIG. 53. A message alert mayalso be used when there is a low flow event that the user is trying tocorrect. In this case, a message alert may be displayed until the lowflow event is cleared to provide feedback to the user on whether theuser fixed the problem.

An “escalating alert” is intended to prompt the user to take action in anon-jarring manner. During an escalating alert, a visual prompt maydisplayed on the touch screen and an audible prompt may be presented(e.g., once). After a given period of time, if the event that caused thealert is not cleared, a more emphatic audible prompt may be presented.If the event causing the alert is not cleared after an additional periodof time, the alert is escalated to a “user alert.” According to oneexemplary implementation of a user alert, a visual prompt is displayeduntil the alert is cleared and an audible prompt, which can be silenced,is presented. The UI subsystem does not handle the transition to fromescalating alert to user alert. Rather, the subsystem that triggered theoriginal event will trigger a new event associated with the user alert.FIG. 54 shows a screen view displaying information concerning anescalating alert. This exemplary alert includes an on-screen alertmessage 400 and a prompt 402 instructing the user to check the drainline for kinks and closed clamps, as well as and an audible prompt. Theaudible prompt may be continuous until it is silenced by the user. FIG.55 shows a screen view including an “audio off” option 404 that may beselected to silence the audible prompt. This alert can be used directly,or as part of the escalating alert scheme.

Each alert/alarm is specified by: an alert/alarm code, which is a uniqueidentifier for the alert/alarm; an alert/alarm name, which is adescriptive name of the alert/alarm; an alert/alarm type, whichcomprises the type of alert or level of alarm; an indication of whetheran audible prompt is associated with the alert/alarm; an indication ofwhether the alert and associated event can be bypassed (or ignored) bythe user; and the event code of the event or events that trigger thealert/alarm.

During alarms, escalating alerts and user alerts, the event code (whichmay be different from the alert or alarm code, as described above) maybe displayed on the screen so that the user can read the code to servicepersonnel if needed. Alternatively or additionally, a voice guidancesystem may be used so that, one connected to a remote call center, thesystem can vocalize pertinent information about the systemconfiguration, state, and error code. The system may be connected to theremote call center via a network, telephonic connection, or some othermeans.

An example of a condition detected by the therapy subsystem is describedbelow in connection with FIG. 56. The condition results when the APDsystem is not positioned on a level surface, which is important for airmanagement. More particularly, the condition results when a tilt sensordetects that APD system is tilted beyond a predetermined threshold, suchas 35°, with respect to a horizontal plane. As described below, arecoverable user alert may be generated by the therapy subsystem if thetilt sensor senses an angle with an absolute value greater than thepredetermined threshold. To avoid nuisance alarms, the user may bedirected to level the APD system before therapy begins. The tiltthreshold may be lower during this pre-therapy period (e.g., 35°). Theuser may also be given feedback concerning whether the problem iscorrected.

When the tilt sensor detects an angle of tilt exceeding a thresholdduring therapy, the machine subsystem 342 responds by stopping the pumpin a similar manner as if it had detected air in the pump chamber. Thetherapy subsystem 340 asks for status and determines that the machinelayer 342 has paused pumping due to tilt. It also receives statusinformation concerning the angle of the machine. At this point, thetherapy subsystem 340 generates a tilt condition, pauses therapy, andsends a command to the machine subsystem 342 to pause pumping. Thiscommand triggers clean-up, such as taking fluid measurement system (FMS)measurements and closing the patient valve. The therapy subsystem 340also starts a timer and sends an auto recoverable tilt condition up tothe UI model 360, which sends the condition to the UI view 338. The UIview 338 maps the condition to an escalating alert. The therapysubsystem 340 continues to monitor the tilt sensor reading and, if itdrops below the threshold, clears the condition and restarts therapy. Ifthe condition does not clear before the timer expires, the therapysubsystem 340 triggers a user recoverable “tilt timeout” condition thatsupersedes the auto-recoverable tilt condition. It sends this conditionto the UI model 360, which sends the condition to the UI view 338. TheUI view 338 maps the condition to a user alert. This condition can notbe cleared until a restart therapy command is received from the UIsubsystem (e.g., the user pressing the resume button). If the tiltsensor reading is below the threshold, the therapy resumes. If it is notbelow the threshold, the therapy layer triggers an auto recoverable tiltcondition and starts the timer.

Screen Display

As discussed previously, the UI view subsystem 338 (FIG. 47) isresponsible for the presentation of the interface to the user. The UIview subsystem is a client of and interfaces with the UI model subsystem360 (FIG. 47) running on the automation computer. For example, the UIview subsystem communicates with the UI model subsystem to determinewhich screen should be displayed to the user at a given time. The UIview may include templates for the screen views, and may handlelocale-specific settings such as display language, skin, audio language,and culturally sensitive animations.

There are three basic types of events that occur in the UI viewsubsystem. These are local screen events that are handled by theindividual screens, model events in which a screen event must propagatedown to the UI model subsystem, and polling events that occur on a timerand query the UI model subsystem for status. A local screen event onlyaffects the UI view level. These events can be local screen transitions(e.g., in the case of multiple screens for a single model state),updates to view settings (e.g., locality and language options), andrequests to play media clips from a given screen (e.g., instructionalanimations or voice prompts). Model events occur when the UI viewsubsystem must consult with the UI model subsystem to determine how tohandle the event. Examples that fall into this category are theconfirmation of therapy parameters or the pressing of the “starttherapy” button. These events are initiated by the UI view subsystem,but are handled in the UI model subsystem. The UI model subsystemprocesses the event and returns a result to the UI view subsystem. Thisresult drives the internal state of the UI view subsystem. Pollingevents occur when a timer generates a timing signal and the UI modelsubsystem is polled. In the case of a polling event, the current stateof the UI view subsystem is sent to the UI model subsystem forevaluation. The UI model subsystem evaluates the state information andreplies with the desired state of the UI view subsystem. This mayconstitute: (1) a state change, e.g., if the major states of the UImodel subsystem and the UI view subsystem are different, (2) a screenupdate, e.g., if values from the UI model subsystem change valuesdisplayed on-screen, or (3) no change in state, e.g., if the state ofthe UI model subsystem and the UI view subsystem are identical. FIG. 57shows the exemplary modules of the UI view subsystem 338 that performthe functions described above.

As shown in FIG. 57, the UI model client module 406 is used tocommunicate events to the UI model. This module 406 is also used to pollthe UI model for the current status. Within a responsive status message,the UI model subsystem may embed a time to be used to synchronize theclocks of the automation computer and the user interface computer.

The global slots module 408 provides a mechanism by which multiplecallback routines (slots) can subscribe to be notified when given events(signals) occur. This is a “many-to-many” relationship, as a slot can bebound to many signals, and likewise a signal can be bound to many slotsto be called upon its activation. The global slots module 408 handlesnon-screen specific slots, such as application level timers for UI modelpolling or button presses that occur outside of the screen (e.g., thevoice prompt button).

The screen list class 410 contains a listing of all screens in the formof templates and data tables. A screen is made up of a template and anassociated data table that will be used to populate that screen. Thetemplate is a window with widgets laid out on it in a generic manner andwith no content assigned to the widgets. The data table includes recordsthat describe the content used to populate the widgets and the state ofthe widgets. A widget state can be checked or unchecked (in the case ofa checkbox style widget), visible or hidden, or enabled or disabled. Thedata table can also describe the action that occurs as a result of abutton press. For example, a button on window ‘A’ derived from template‘1’ could send an event down to the UI model, whereas that same buttonon window ‘B’ also derived from template ‘1’ could simply cause a localscreen transition without propagating the event down to the UI model.The data tables may also contain an index into the context-sensitivehelp system.

The screen list class 410 forwards data from the UI model to theintended screen, selects the proper screen-based data from the UI model,and displays the screen. The screen list class 410 selects which screento display based on two factors: the state reported by the UI model andthe internal state of the UI view. In some cases, the UI model may onlyinform the UI view that it is allowed to display any screen within acategory. For example, the model may report that the machine is idle(e.g., no therapy has been started or the setup phase has not yetoccurred). In this case, it is not necessary to confer with the UI modelwhen the user progresses from a menu into its sub-menu. To track thechange, the UI view will store the current screen locally. This localsequencing of screens is handled by the table entries described above.The table entry lists the actions that respective buttons will initiatewhen pressed.

The language manager class 412 is responsible for performing inventoryon and managing translations. A checksum may be performed on the list ofinstalled languages to alert the UI view if any of the translations arecorrupted and or missing. Any class that wants a string translated asksthe language manager class 412 to perform it. Translations may behandled by a library (e.g., Qt®). Preferably, translations are requestedas close as possible to the time of rendering. To this end, most screentemplate member access methods request a translation right beforehanding it to the widget for rendering.

A skin comprises a style-sheet and images that determine the “look andfeel” of the user interface. The style-sheet controls things such asfonts, colors, and which images a widget will use to display its variousstates (normal, pressed, disabled, etc.). Any displayed widget can haveits appearance altered by a skin change. The skin manager module 414 isresponsible for informing the screen list and, by extension, the screenwidgets, which style-sheet and skin graphics should be displayed. Theskin manager module 414 also includes any animated files the applicationmay want to display. On a skin change event, the skin manager willupdate the images and style-sheet in the working set directory with theproper set, which is retrieved from an archive.

The video manager module 416 is responsible for playinglocale-appropriate video given a request to display a particular video.On a locale change event, the video manager will update the videos andanimations in the working set directory with the proper set from anarchive. The video manager will also play videos that have accompanyingaudio in the audio manager module 418. Upon playback of these videos,the video manager module 416 will make the appropriate request to theaudio manager module 418 to play the recording that belongs to theoriginally requested video clip.

Similarly, the audio manager module 418 is responsible for playinglocale-appropriate audio given a request to play a particular audioclip. On a locale change event, the audio manager will update the audioclips in the working set directory with the proper set from an archive.The audio manager module 418 handles all audio initiated by the UI view.This includes dubbing for animations and sound clips for voice prompts.

The database client module 420 is used to communicate with the databasemanager process, which handles the interface between the UI viewsubsystem and the database server 366 (FIG. 47). The UI view uses thisinterface to store and retrieve settings, and to supplement therapy logswith user-provided answers to questions about variables (e.g., weightand blood pressure).

The help manager module 422 is used to manage the context-sensitive helpsystem. Each page in a screen list that presents a help button mayinclude an index into the context-sensitive help system. This index isused so that the help manager can display the help screen associatedwith a page. The help screen may include text, pictures, audio, andvideo.

The auto ID manager 424 is called upon during pre-therapy setup. Thismodule is responsible for capturing an image (e.g., a photographicimage) of a solution bag code (e.g., a datamatrix code). The dataextracted from the image is then sent to the machine control subsystemto be used by the therapy subsystem to identify the contents of asolution bag, along with any other information (e.g., origin) includedin the code.

Using the modules described above, the UI view subsystem 338 renders thescreen views that are displayed to the user via the user interface(e.g., display 324 of FIG. 45). FIGS. N-T show exemplary screen viewsthat may be rendered by the UI view subsystem. These screen viewsillustrate, for example, exemplary input mechanisms, display formats,screen transitions, icons and layouts. Although the screens shown aregenerally displayed during or before therapy, aspects of the screenviews may be used for different input and output functions than thoseshown.

The screen shown in FIG. 58 is an initial screen that provides the userthe option of selecting between “start therapy” 426 to initiate thespecified therapy 428 or “settings” 430 to change settings. Icons 432and 434 are respectively provided to adjust brightness and audio levels,and an information icon 436 is provided to allow the user to solicitmore information. These icons may appear on other screens in a similarmanner.

FIG. 59 shows a status screen that provides information the status ofthe therapy. In particular, the screen indicates the type of therapybeing performed 438, the estimated completion time 440, and the currentfill cycle number and total number of fill cycles 442. The completionpercentage of the current fill cycle 444 and the completion percentageof the total therapy 446 are both numerically and graphically displayed.The user may select a “pause” option 448 to pause therapy.

FIG. 60 shows a menu screen with various comfort settings. The menuincludes brightness arrows 450, volume arrows 452 and temperature arrows454. By selecting either the up or down arrow in each respective pair, auser can increase or decrease screen brightness, audio volume, and fluidtemperature. The current brightness percentage, volume percentage andtemperature are also displayed. When the settings are as desired, a usermay select the “OK” button 456.

FIG. 61 shows a help menu, which may be reached, for example, bypressing a help or information button on a prior screen. The help menumay include text 458 and/or an illustration 460 to assist the user. Thetext and/or illustration may be “context sensitive,” or based on thecontext of the prior screen. If the information provided to the usercannot conveniently be provided in one screen, for example in the caseof a multi-step process, arrows 462 may be provided to allow the user tonavigate backward and forward between a series of screens. When the userhas obtained the desired information. he or she may select the “back”button 464. If additional assistance is required, a user may select the“call service center” option 466 to have the system contact the callservice center.

FIG. 62 illustrates a screen that allows a user to set a set ofparameters. For example, the screen displays the current therapy mode468 and minimum drain volume 470, and allows a user to select theseparameters to be changed. Parameters may be changed in a number of ways,such as by selecting a desired option from a round robin style menu onthe current screen. Alternatively, when the user selects a parameter tobe changed, a new screen may appear, such as that shown in FIG. 63. Thescreen of FIG. 63 allows a user to adjust the minimum drain volume byinputting a numeric value 472 using a keypad 474. Once entered, the usermay confirm or cancel the value using buttons 476 and 478. Referringagain to FIG. 62, a user may then use the “back” and “next” arrows 480,482 to navigate through a series of parameters screens, each including adifferent set of parameters.

Once all desired parameters have been set or changed (e.g., when theuser has navigated through the series of parameters screens), a screensuch as that shown in FIG. 64 may be presented to allow a user to reviewand confirm the settings. Parameters that have changed may optionally behighlighted in some fashion to draw the attention of the user. When thesettings are as desired, a user may select the “confirm” button 486.

While aspects of the invention have been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, embodiments of the invention as set forth herein areintended to be illustrative, not limiting. Various changes may be madewithout departing from the spirit and scope of the invention.

The invention claimed is:
 1. A medical infusion fluid handling system,comprising: a carriage arranged to receive a plurality of solution lineseach having a connector end and a cap, the carriage being arranged tomove along a first linear path so as to move the connector ends of thesolution lines along the first linear path; and a cap stripper arrangedto engage with the caps on the solution lines on the carriage, the capstripper being arranged to move in a second linear path transverse tothe first linear path and to move with the carriage along the firstlinear path; a housing and a door that is movably mounted to thehousing; wherein the carriage is mounted to the door, and is mounted tomove along rails extending along a length of the door.
 2. The system ofclaim 1, further comprising a carriage drive mounted to the housing,wherein the carriage drive engages the carriage when the door is movedto a closed position, and disengages from the carriage when the door ismoved to an open position.
 3. The system of claim 2, wherein the capstripper is mounted to the housing and is engageable with the carriagedrive to move in the first linear path with the carriage drive.
 4. Thesystem of claim 3, wherein the cap stripper includes a plurality offork-shaped elements arranged to engage with a corresponding cap on asolution line carried by the carriage.
 5. The system of claim 4, whereineach of the fork-shaped elements is arranged to resist movement of thecorresponding cap along the first linear path when engaged with thecorresponding cap.
 6. The system of claim 5, wherein the carriage isarranged to move the solution lines and the caps along the first linearpath such that the caps receive a corresponding spike cap on a fluidhandling cassette mounted on the door.
 7. The system of claim 6, whereinthe cap stripper is arranged to move in the second linear path to engagethe fork-shaped elements with corresponding caps after each said cap hasreceived the corresponding spike cap.
 8. The system of claim 7, whereinthe cap stripper is arranged to move with the carriage along the firstlinear path away from the cassette with the fork-shaped elements engagedwith the corresponding caps so as to remove spike caps from the fluidhandling cassette.
 9. The system of claim 8, wherein the cap stripper isarranged to stop movement along the first linear path while the carriagecontinues to move away from the fluid handling cassette so as to removethe caps from the solution lines carried by the carriage.
 10. The systemof claim 9, wherein the cap stripper is arranged to move in the secondlinear path to clear a path for the carriage and allow the carriage tomove along the first linear path toward the fluid handling cassette toengage the connector ends of the solution lines with spikes exposed onthe fluid handling cassette as a result of removal of the spike capsfrom the fluid handling cassette.
 11. The system of claim 10, whereinthe cap stripper includes a stripper element mounted to a cap stripperhousing, and the stripper element is moveable along the second linearpath relative to the cap stripper housing.
 12. The system of claim 11,wherein the cap stripper includes a pneumatic bladder arranged to movethe stripper element along the second linear path relative to the capstripper housing.
 13. The system of claim 2, wherein the carriage driveincludes a drive element and a pneumatic bladder or a screw drive tomove the drive element along the first linear path.
 14. The system ofclaim 13, wherein the drive element includes two tabs that engage withcorresponding slots of the carriage.
 15. A medical infusion fluidhandling system, comprising: a carriage arranged to receive a pluralityof solution lines each having a connector end and a cap, the carriagebeing arranged to move each said solution line, each said connector endand each said cap of said plurality of solution lines along a firstlinear path so as to connect each said cap directly to a correspondingspike cap on a fluid handling cassette; a cap stripper arranged toengage with the caps on the solution lines on the carriage, the capstripper being arranged to move in a second linear path transverse tothe first linear path and. to move with the carriage along the firstlinear path; and a housing and a door that is movably mounted to thehousing, wherein the carriage is mounted to the door and is mounted tomove along rails extending along a length of the door.
 16. The system ofclaim 15, further comprising a carriage drive mounted to the housing,wherein the carriage drive engages the carriage when the door is movedto a closed position, and disengages from the carriage when the door ismoved to an open position.
 17. The system of claim 16, wherein the capstripper is mounted to the housing and is engageable with the carriagedrive to move in the first linear path with the carriage drive.
 18. Thesystem of claim 17, wherein the cap stripper includes a plurality offork-shaped elements arranged to engage with a corresponding cap on asolution line carried by the carriage.
 19. The system of claim 18,wherein each of the fork-shaped elements is arranged to resist movementof the corresponding cap along the first linear path when engaged withthe corresponding cap.
 20. The system of claim 19, wherein the carriageis arranged to move the solution lines and the caps along the firstlinear path such that the caps receive the corresponding spike cap onthe fluid handling cassette mounted on the door.
 21. The system of claim20, wherein the cap stripper is arranged to move in the second linearpath to engage the fork-shaped elements with corresponding caps aftereach said cap has received the corresponding spike cap.
 22. The systemof claim 21, wherein the cap stripper is arranged to move with thecarriage along the first linear path away from the cassette with thefork-shaped elements engaged with the corresponding caps so as to removespike caps from the cassette.
 23. The system of claim 22, wherein thecap stripper is arranged to stop movement along the first linear pathwhile the carriage continues to move away from the cassette so as toremove the caps from the solution lines carried by the carriage.
 24. Thesystem of claim 23, wherein the cap stripper is arranged to move in thesecond linear path to clear a path for the carriage and allow thecarriage to move along the first linear path toward the cassette toengage the connector ends of the solution lines with spikes exposed onthe cassette as a result of removal of the spike caps from the cassette.25. The system of claim 24, wherein the cap stripper includes a stripperelement mounted to a cap stripper housing, and the stripper element ismoveable along the second linear path relative to the cap stripperhousing.
 26. The system of claim 25, wherein the cap stripper includes apneumatic bladder arranged to move the stripper element along the secondlinear path relative to the cap stripper housing.
 27. The system ofclaim 16, wherein the carriage drive includes a drive element and apneumatic bladder or a screw drive to move the drive element along thefirst linear path.
 28. The system of claim 27, wherein the drive elementincludes two tabs that engage with corresponding slots of the carriage.29. The system of claim 15, wherein the cap stripper includes aplurality of rocker arms each associated with a fork-shaped element,each of the rocker arms being arranged to move to engage thecorresponding spike cap.
 30. The system of claim 29, wherein each of therocker arms is arranged to engage with the corresponding spike cap onlywhen an associated fork-shaped element engages with a cap on a solutionline.
 31. The system of claim 30, wherein each rocker arm is pivotallymounted to the cap stripper and includes a solution line cap engagementportion and a spike cap engagement portion, each rocker arm pivoting toengage the spike cap when the solution line cap engagement portioncontacts the cap on the solution line.